Changes for 1.1

1.1.2 (Jul 21, 2016)

  • Python 2: sendall on a non-blocking socket could spuriously fail with a timeout.

  • If sys.stderr has been monkey-patched (not recommended), exceptions that the hub reports aren’t lost and can still be caught. Reported in issue #825 by Jelle Smet.

  • selectors.SelectSelector is properly monkey-patched regardless of the order of imports. Reported in issue #835 by Przemysław Węgrzyn.

  • Python 2: reload(site) no longer fails with a TypeError if gevent has been imported. Reported in issue #805 by Jake Hilton.

1.1.1 (Apr 4, 2016)

1.1.0 (Mar 5, 2016)

  • Python 3: A monkey-patched threading.RLock now properly blocks (or deadlocks) in acquire if the default value for timeout of -1 is used (which differs from gevent’s default of None). The acquire method also raises the same ValueError exceptions that the standard library does for invalid parameters. Reported in issue #750 by Joy Zheng.

  • Fix a race condition in Event that made it return False when the event was set and cleared by the same greenlet before allowing a switch to already waiting greenlets. (Found by the 3.4 and 3.5 standard library test suites; the same as Python bug 13502. Note that the Python 2 standard library still has this race condition.)

  • Event and AsyncResult now wake waiting greenlets in the same (unspecified) order. Previously, AsyncResult tended to use a FIFO order, but this was never guaranteed. Both classes also use less per-instance memory.

  • Using a Logger as a pywsgi error or request log stream no longer produces extra newlines. Reported in issue #756 by ael-code.

  • Windows: Installing from an sdist (.tar.gz) on PyPI no longer requires having Cython installed first. (Note that the binary installation formats (wheels, exes, msis) are preferred on Windows.) Reported in issue #757 by Ned Batchelder.

  • Issue a warning when patch_all() is called with os set to False (not the default) but signal is still True (the default). This combination of parameters will cause signal handlers for SIGCHLD to not get called. In the future this might raise an error. Reported by Josh Zuech.

  • Issue a warning when patch_all() is called more than once with different arguments. That causes the cumulative set of all True arguments to be patched, which may cause unexpected results.

  • Fix returning the original values of certain threading attributes from gevent.monkey.get_original().

1.1rc5 (Feb 24, 2016)

  • SSL: Attempting to send empty data using the sendall() method of a gevent SSL socket that has a timeout now returns immediately (like the standard library does), instead of incorrectly raising ssl.SSLEOFError. (Note that sending empty data with the send() method does raise SSLEOFError in both gevent and the standard library.) Reported in issue #719 by Mustafa Atik and Tymur Maryokhin, with a reproducible test case provided by Timo Savola.

1.1rc4 (Feb 16, 2016)

  • Python 2: Using the blocking API at import time when multiple greenlets are also importing should not lead to LoopExit. Reported in issue #728 by Garrett Heel.

  • Python 2: Don’t raise OverflowError when using the readline method of the WSGI input stream without a size hint or with a large size hint when the client is uploading a large amount of data. (This only impacted CPython 2; PyPy and Python 3 already handled this.) Reported in issue #289 by ggjjlldd, with contributions by Nathan Hoad.

  • BaseServer and its subclasses like WSGIServer avoid allocating a new closure for each request, reducing overhead.

  • Python 2: Under 2.7.9 and above (or when the PEP 466 SSL interfaces are available), perform the same hostname validation that the standard library does; previously this was skipped. Also, reading, writing, or handshaking a closed SSLSocket now raises the same ValueError the standard library does, instead of an AttributeError. Found by updating gevent’s copy of the standard library test cases. Initially reported in issue #735 by Dmitrij D. Czarkoff.

  • Python 3: Fix unwrap() and SNI callbacks. Also raise the correct exceptions for unconnected SSL sockets and properly validate SSL hostnames. Found via updated standard library tests.

  • Python 3: Add missing support for socket.socket.sendfile(). Found via updated standard library tests.

  • Python 3.4+: Add missing support for socket.socket.get_inheritable() and set_inheritable(). Found via updated standard library tests.

1.1rc3 (Jan 04, 2016)

  • Python 2: Support the new PEP 466 ssl interfaces on any Python 2 version that supplies them, not just on the versions it officially shipped with. Some Linux distributions, including RedHat/CentOS and Amazon have backported the changes to older versions. Reported in issue #702.

  • PyPy: An interaction between Cython compiled code and the garbage collector caused PyPy to crash when a previously-allocated Semaphore was used in a __del__ method, something done in the popular libraries requests and urllib3. Due to this and other Cython related issues, the Semaphore class is no longer compiled by Cython on PyPy. This means that it is now traceable and not exactly as atomic as the Cython version, though the overall semantics should remain the same. Reported in issue #704 by Shaun Crampton.

  • PyPy: Optimize the CFFI backend to use less memory (two pointers per watcher).

  • Python 3: The WSGI PATH_INFO entry is decoded from URL escapes using latin-1, not UTF-8. This improves compliance with PEP 3333 and compatibility with some frameworks like Django. Fixed in pull request #712 by Ruben De Visscher.

1.1rc2 (Dec 11, 2015)

  • Exceptions raised by gevent’s SSL sockets are more consistent with the standard library (e.g., gevent’s Python 3 SSL sockets raise socket.timeout instead of ssl.SSLError, a change introduced in Python 3.2).

  • Python 2: gevent’s socket’s sendall method could completely ignore timeouts in some cases. The timeout now refers to the total time taken by sendall.

  • gevent’s SSL socket’s sendall method should no longer raise SSL3_WRITE_PENDING in rare cases when sending large buffers. Reported in issue #317.

  • gevent.signal.signal() now allows resetting (SIG_DFL) and ignoring (SIG_IGN) the SIGCHLD signal at the process level (although this may allow race conditions with libev child watchers). Reported in issue #696 by Adam Ning.

  • gevent.spawn_raw() now accepts keyword arguments, as previously (incorrectly) documented. Reported in issue #680 by Ron Rothman.

  • PyPy: PyPy 2.6.1 or later is now required (4.0.1 or later is recommended).

  • The CFFI backend is now built and usable on CPython implementations (except on Windows) if cffi is installed before gevent is installed. To use the CFFI backend, set the environment variable GEVENT_CORE_CFFI_ONLY before starting Python. This can aid debugging in some cases and helps ensure parity across all combinations of supported platforms.

  • The CFFI backend now calls the callback of a watcher whose args attribute is set to None, just like the Cython backend does. It also only allows args to be a tuple or None, again matching the Cython backend.

  • PyPy/CFFI: Fix a potential crash when using stat watchers.

  • PyPy/CFFI: Encode unicode paths for stat watchers using sys.getfilesystemencoding() like the Cython backend.

  • The internal implementation modules gevent._fileobject2, gevent._fileobject3, and gevent._util were removed. These haven’t been used or tested since 1.1b1.

1.1rc1 (Nov 14, 2015)

  • Windows/Python 3: Finish porting the gevent.subprocess module, fixing a large number of failing tests. Examples of failures are in issue #668 and issue #669 reported by srossross.

  • Python 3: The SSLSocket class should return an empty bytes object on an EOF instead of a str. Fixed in pull request #674 by Dahoon Kim.

  • Python 2: Workaround a buffering bug in the stdlib io module that caused FileObjectPosix to be slower than necessary in some cases. Reported in issue #675 by WGH-.

  • PyPy: Fix a crash. Reported in issue #676 by Jay Oster.

    Caution

    There are some remaining, relatively rare, PyPy crashes, but their ultimate cause is unknown (gevent, CFFI, greenlet, the PyPy GC?). PyPy users can contribute to issue #677 to help track them down.

  • PyPy: Exceptions raised while handling an error raised by a loop callback function behave like the CPython implementation: the exception is printed, and the rest of the callbacks continue processing.

  • If a Hub object with active watchers was destroyed and then another one created for the same thread, which itself was then destroyed with destroy_loop=True, the process could crash. Documented in issue #237 and fix based on pull request #238, both by Jan-Philip Gehrcke.

  • Python 3: Initializing gevent’s hub for the first time simultaneously in multiple native background threads could fail with AttributeError and ImportError. Reported in issue #687 by Gregory Petukhov.

1.1b6 (Oct 17, 2015)

  • PyPy: Fix a memory leak for code that allocated and disposed of many gevent.lock.Semaphore subclasses. If monkey-patched, this could also apply to threading.Semaphore objects. Reported in issue #660 by Jay Oster.

  • PyPy: Cython version 0.23.4 or later must be used to avoid a memory leak (details). Thanks to Jay Oster.

  • Allow subclasses of WSGIHandler to handle invalid HTTP client requests. Reported by not-bob.

  • WSGIServer more robustly supports Logger-like parameters for log and error_log (as introduced in 1.1b1, this could cause integration issues with gunicorn). Reported in issue #663 by Jay Oster.

  • _DummyThread objects, created in a monkey-patched system when threading.current_thread() is called in a new greenlet (which often happens implicitly, such as when logging) are much lighter weight. For example, they no longer allocate and then delete a Semaphore, which is especially important for PyPy.

  • Request logging by gevent.pywsgi formats the status code correctly on Python 3. Reported in issue #664 by Kevin Chen.

  • Restore the ability to take a weak reference to instances of exactly gevent.lock.Semaphore, which was unintentionally removed as part of making Semaphore atomic on PyPy on 1.1b1. Reported in issue #666 by Ivan-Zhu.

  • Build Windows wheels for Python 3.5. Reported in pull request #665 by Hexchain Tong.

1.1b5 (Sep 18, 2015)

  • gevent.subprocess works under Python 3.5. In general, Python 3.5 has preliminary support. Reported in issue #653 by Squeaky.

  • Popen.communicate honors a timeout argument even if there is no way to communicate with the child process (none of stdin, stdout and stderr were set to PIPE). Noticed as part of the Python 3.5 test suite for the new function subprocess.run but impacts all versions (timeout is an official argument under Python 3 and a gevent extension with slightly different semantics under Python 2).

  • Fix a possible ValueError from Queue.peek. Reported in issue #647 by Kevin Chen.

  • Restore backwards compatibility for using gevent.signal as a callable, which, depending on the order of imports, could be broken after the addition of the gevent.signal module. Reported in issue #648 by Sylvain Zimmer.

  • gevent blocking operations performed at the top-level of a module after the system was monkey-patched under Python 2 could result in raising a LoopExit instead of completing the expected blocking operation. Note that performing gevent blocking operations in the top-level of a module is typically not recommended, but this situation can arise when monkey-patching existing scripts. Reported in issue #651 and issue #652 by Mike Kaplinskiy.

  • SIGCHLD and waitpid now work for the pids returned by the (monkey-patched) os.forkpty and pty.fork functions in the same way they do for the os.fork function. Reported in issue #650 by Erich Heine.

  • WSGIServer and WSGIHandler do a better job detecting and reporting potential encoding errors for headers and the status line during start_response() as recommended by the WSGI specification. In addition, under Python 2, unnecessary encodings and decodings (often a trip through the ASCII encoding) are avoided for conforming applications. This is an enhancement of an already documented and partially enforced constraint: beginning in 1.1a1, under Python 2, u'abc' would typically previously have been allowed, but u'\u1f4a3' would not; now, neither will be allowed, more closely matching the specification, improving debugability and performance and allowing for better error handling both by the application and by gevent (previously, certain encoding errors could result in gevent writing invalid/malformed HTTP responses). Reported by Greg Higgins and Carlos Sanchez.

  • Code coverage by tests is now reported on coveralls.io.

1.1b4 (Sep 4, 2015)

  • Detect and raise an error for several important types of programming errors even if Python interpreter optimizations are enabled with -O or PYTHONOPTIMIZE. Previously these would go undetected if optimizations were enabled, potentially leading to erratic, difficult to debug behaviour.

  • Fix an AttributeError from gevent.queue.Queue when peek was called on an empty Queue. Reported in issue #643 by michaelvol.

  • Make SIGCHLD handlers specified to gevent.signal.signal() work with the child watchers that are used by default. Also make gevent.os.waitpid() work with a first argument of -1. (Also applies to the corresponding monkey-patched stdlib functions.) Noted by users of gunicorn.

  • Under Python 2, any timeout set on a socket would be ignored when using the results of socket.makefile. Reported in issue #644 by Karan Lyons.

1.1b3 (Aug 16, 2015)

  • Fix an AttributeError from gevent.monkey.patch_builtins on Python 2 when the future library is also installed. Reported by Carlos Sanchez.

  • PyPy: Fix a DistutilsModuleError or ImportError if the CFFI module backing gevent.core needs to be compiled when the hub is initialized (due to a missing or invalid __pycache__ directory). Now, the module will be automtically compiled when gevent is imported (this may produce compiler output on stdout). Reported in issue #619 by Thinh Nguyen and issue #631 by Andy Freeland, with contributions by Jay Oster and Matt Dupre.

  • PyPy: Improve the performance of gevent.socket.socket:sendall with large inputs. bench_sendall.py now performs about as well on PyPy as it does on CPython, an improvement of 10x (from ~60MB/s to ~630MB/s). See this pypy bug for details.

  • Fix a possible TypeError when calling gevent.socket.wait. Reported in #635 by lanstin.

  • gevent.socket.socket:sendto properly respects the socket’s blocking status (meaning it can raise EWOULDBLOCK now in cases it wouldn’t have before). Reported in pull request #634 by Mike Kaplinskiy.

  • Common lookup errors using the threaded resolver are no longer always printed to stderr since they are usually out of the programmer’s control and caught explicitly. (Programming errors like TypeError are still printed.) Reported in issue #617 by Jay Oster and Carlos Sanchez.

  • PyPy: Fix a TypeError from gevent.idle(). Reported in issue #639 by chilun2008.

  • The imap_unordered() methods of a pool-like object support a maxsize parameter to limit the number of results buffered waiting for the consumer. Reported in issue #638 by Sylvain Zimmer.

  • The class gevent.queue.Queue now consistently orders multiple blocked waiting put and get callers in the order they arrived. Previously, due to an implementation quirk this was often roughly the case under CPython, but not under PyPy. Now they both behave the same.

  • The class gevent.queue.Queue now supports the len() function.

1.1b2 (Aug 5, 2015)

  • Enable using the c-ares resolver under PyPy. Note that its performance characteristics are probably sub-optimal.

  • On some versions of PyPy on some platforms (notably 2.6.0 on 64-bit Linux), enabling gevent.monkey.patch_builtins could cause PyPy to crash. Reported in issue #618 by Jay Oster.

  • gevent.kill() raises the correct exception in the target greenlet. Reported in issue #623 by Jonathan Kamens.

  • Various fixes on Windows. Reported in issue #625, issue #627, and issue #628 by jacekt and Yuanteng (Jeff) Pei. Fixed in pull request #624.

  • Add readable() and writable() methods to FileObjectPosix; this fixes e.g., help() on Python 3 when monkey-patched.

1.1b1 (Jul 17, 2015)

  • setup.py can be run from a directory containing spaces. Reported in issue #319 by Ivan Smirnov.

  • setup.py can build with newer versions of clang on OS X. They enforce the distinction between CFLAGS and CPPFLAGS.

  • gevent.lock.Semaphore is atomic on PyPy, just like it is on CPython. This comes at a small performance cost on PyPy.

  • Fixed regression that failed to set the successful value to False when killing a greenlet before it ran with a non-default exception. Fixed in pull request #608 by Heungsub Lee.

  • libev’s child watchers caused os.waitpid() to become unreliable due to the use of signals on POSIX platforms. This was especially noticeable when using gevent.subprocess in combination with multiprocessing. Now, the monkey-patched os module provides a waitpid() function that seeks to ameliorate this. Reported in issue #600 by champax and issue #452 by Łukasz Kawczyński.

  • On platforms that implement select.poll, provide a gevent-friendly gevent.select.poll and corresponding monkey-patch. Implemented in pull request #604 by Eddi Linder.

  • Allow passing of events to the io callback under PyPy. Reported in issue #531 by M. Nunberg and implemented in pull request #604.

  • gevent.thread.allocate_lock() (and so a monkey-patched standard library allocate_lock()) more closely matches the behaviour of the builtin: an unlocked lock cannot be released, and attempting to do so throws the correct exception (thread.error on Python 2, RuntimeError on Python 3). Previously, over-releasing a lock was silently ignored. Reported in issue #308 by Jędrzej Nowak.

  • gevent.fileobject.FileObjectThread uses the threadpool to close the underling file-like object. Reported in issue #201 by vitaly-krugl.

  • Malicious or malformed HTTP chunked transfer encoding data sent to the pywsgi handler is handled more robustly, resulting in “HTTP 400 bad request” responses instead of a 500 error or, in the worst case, a server-side hang. Reported in issue #229 by Björn Lindqvist.

  • Importing the standard library threading module before using gevent.monkey.patch_all() no longer causes Python 3.4 to fail to get the repr of the main thread, and other CPython platforms to return an unjoinable DummyThread. (Note that this is not recommended.) Reported in issue #153.

  • Under Python 2, use the io package to implement FileObjectPosix. This unifies the code with the Python 3 implementation, and fixes problems with using seek(). See issue #151.

  • Under Python 2, importing a module that uses gevent blocking functions at its top level from multiple greenlets no longer produces import errors (Python 3 handles this case natively). Reported in issue #108 by shaun and initial fix based on code by Sylvain Zimmer.

  • gevent.spawn(), spawn_raw() and spawn_later(), as well as the Greenlet constructor, immediately produce useful TypeErrors if asked to run something that cannot be run. Previously, the spawned greenlet would die with an uncaught TypeError the first time it was switched to. Reported in issue #119 by stephan.

  • Recursive use of ThreadPool.apply no longer raises a LoopExit error (using ThreadPool.spawn and then get on the result still could; you must be careful to use the correct hub). Reported in issue #131 by 8mayday.

  • When the threading module is monkey-patched, the module-level lock in the logging module is made greenlet-aware, as are the instance locks of any configured handlers. This makes it safer to import modules that use the standard pattern of creating a module-level Logger instance before monkey-patching. Configuring logging with a basic configuration and then monkey-patching is also safer (but not configurations that involve such things as the SocketHandler).

  • Fix monkey-patching of threading.RLock under Python 3.

  • Under Python 3, monkey-patching at the top-level of a module that was imported by another module could result in a RuntimeError from importlib. Reported in issue #615 by Daniel Mizyrycki. (The same thing could happen under Python 2 if a threading.RLock was held around the monkey-patching call; this is less likely but not impossible with import hooks.)

  • Fix configuring c-ares for a 32-bit Python when running on a 64-bit platform. Reported in issue #381 and fixed in pull request #616 by Chris Lane. Additional fix in pull request #626 by Kevin Chen.

  • (Experimental) Let the pywsgi.WSGIServer accept a logging.Logger instance for its log and (new) error_log parameters. Take care that the system is fully monkey-patched very early in the process’s lifetime if attempting this, and note that non-file handlers have not been tested. Fixes issue #106.

1.1a2 (Jul 8, 2015)

  • gevent.threadpool.ThreadPool.imap and imap_unordered now accept multiple iterables.

  • (Experimental) Exceptions raised from iterating using the ThreadPool or Group mapping/application functions should now have the original traceback.

  • gevent.threadpool.ThreadPool.apply() now raises any exception raised by the called function, the same as Group/Pool and the builtin apply() function. This obsoletes the undocumented apply_e function. Original PR issue #556 by Robert Estelle.

  • Monkey-patch the selectors module from patch_all and patch_select on Python 3.4. See issue #591.

  • Additional query functions for the gevent.monkey module allow knowing what was patched. Discussed in issue #135 and implemented in pull request #325 by Nathan Hoad.

  • In non-monkey-patched environments under Python 2.7.9 or above or Python 3, using a gevent SSL socket could cause the greenlet to block. See issue #597 by David Ford.

  • gevent.socket.socket.sendall() supports arbitrary objects that implement the buffer protocol (such as ctypes structures), just like native sockets. Reported in issue #466 by tzickel.

  • Added support for the onerror attribute present in CFFI 1.2.0 for better signal handling under PyPy. Thanks to Armin Rigo and Omer Katz. (See https://bitbucket.org/cffi/cffi/issue/152/handling-errors-from-signal-handlers-in)

  • The gevent.subprocess module is closer in behaviour to the standard library under Python 3, at least on POSIX. The pass_fds, restore_signals, and start_new_session arguments are now implemented, as are the timeout parameters to various functions. Under Python 2, the previously undocumented timeout parameter to Popen.communicate raises an exception like its Python 3 counterpart.

  • An exception starting a child process with the gevent.subprocess module no longer leaks file descriptors. Reported in pull request #374 by 陈小玉.

  • The example echoserver.py no longer binds to the standard X11 TCP port. Reported in issue #485 by minusf.

  • gevent.iwait() no longer throws LoopExit if the caller switches greenlets between return values. Reported and initial patch in issue #467 by Alexey Borzenkov.

  • The default threadpool and default threaded resolver work in a forked child process, such as with multiprocessing.Process. Previously the child process would hang indefinitely. Reported in issue #230 by Lx Yu.

  • Fork watchers are more likely to (eventually) get called in a multi-threaded program (except on Windows). See issue #154.

  • gevent.killall() accepts an arbitrary iterable for the greenlets to kill. Reported in issue #404 by Martin Bachwerk; seen in combination with older versions of simple-requests.

  • gevent.local.local objects are now eligible for garbage collection as soon as the greenlet finishes running, matching the behaviour of the built-in threading.local (when implemented natively). Reported in issue #387 by AusIV.

  • Killing a greenlet (with gevent.kill() or gevent.Greenlet.kill()) before it is actually started and switched to now prevents the greenlet from ever running, instead of raising an exception when it is later switched to. See issue #330 reported by Jonathan Kamens.

1.1a1 (Jun 29, 2015)

  • Add support for Python 3.3 and 3.4. Many people have contributed to this effort, including but not limited to Fantix King, hashstat, Elizabeth Myers, jander, Luke Woydziak, and others. See issue #38.

  • Add support for PyPy. See issue #248. Note that for best results, you’ll need a very recent PyPy build including CFFI 1.2.0.

  • Drop support for Python 2.5. Python 2.5 users can continue to use gevent 1.0.x.

  • Fix gevent.joinall() to not ignore count when raise_error is False. See pull request #512 by Ivan Diao.

  • Fix gevent.subprocess.Popen to not ignore the bufsize argument. Note that this changes the (platform dependent) default, typically from buffered to unbuffered. See pull request #542 by Romuald Brunet.

  • Upgraded c-ares to 1.10.0. See pull request #579 by Omer Katz.

    Caution

    The c-ares configure script is now more strict about the contents of environment variables such as CFLAGS and LDFLAGS and they may have to be modified (for example, CFLAGS is no longer allowed to include -I directives, which must instead be placed in CPPFLAGS).

  • Add a count argument to gevent.iwait(). See pull request #482 by wiggin15.

  • Add a timeout argument to gevent.queue.JoinableQueue.join() which now returns whether all items were waited for or not.

  • gevent.queue.JoinableQueue treats items passed to __init__ as unfinished tasks, the same as if they were put. Initial pull request #554 by DuLLSoN.

  • gevent.pywsgi no longer prints debugging information for the normal conditions of a premature client disconnect. See issue #136, fixed in pull request #377 by Paul Collier.

  • (Experimental.) Waiting on or getting results from greenlets that raised exceptions now usually raises the original traceback. This should assist things like Sentry to track the original problem. See issue #450 and issue #528 by Rodolfo and Eddi Linder and issue #240 by Erik Allik.

  • Upgrade to libev 4.20. See pull request #590 by Peter Renström.

  • Fix gevent.baseserver.BaseServer to be printable when its handle function is an instancemethod of itself. See pull request #501 by Joe Jevnik.

  • Make the acquire method of gevent.lock.DummySemaphore always return True, supporting its use-case as an “infinite” or unbounded semaphore providing no exclusion, and allowing the idiom if sem.acquire(): .... See pull request #544 by Mouad Benchchaoui.

  • Patch subprocess by default in gevent.monkey.patch_all. See issue #446.

  • gevent.pool.Group.imap and imap_unordered now accept multiple iterables like itertools.imap. issue #565 reported by Thomas Steinacher.

  • Compatibility note: gevent.baseserver.BaseServer and its subclass gevent.server.StreamServer now deterministically close the client socket when the request handler returns. Previously, the socket was left at the mercies of the garbage collector; under CPython 2.x this meant when the last reference went away, which was usually, but not necessarily, when the request handler returned, but under PyPy it was some arbitrary point in the future and under CPython 3.x a ResourceWarning could be generated. This was undocumented behaviour, and the client socket could be kept open after the request handler returned either accidentally or intentionally.

  • Compatibility note: pywsgi now ensures that headers can be encoded in latin-1 (ISO-8859-1). This improves adherence to the HTTP standard (and is necessary under Python 3). Under certain conditions, previous versions could have allowed non-ISO-8859-1 headers to be sent, but their interpretation by a conforming recipient is unknown; now, a UnicodeError will be raised. See issue #614.