Rather than silently producing a class that doesn't support zero-argument super() in methods, failing to pass the new __classcell__ namespace entry up to type.__new__ now results in a DeprecationWarning and a class that supports zero-argument super().
Modifying the class __dict__ inside the __set_name__ method of a descriptor that is used inside that class no longer prevents calling the __set_name__ method of other descriptors.
Fix a bug in the implementation yield from when checking if the next instruction is YIELD_FROM. Regression introduced by WORDCODE (issue #26647).
Unknown escapes in re.sub() replacement template are allowed again. But they still are deprecated and will be disabled in 3.7.
Fix a regression introduced in warnings.catch_warnings(): call warnings.showwarning() if it was overridden inside the context manager.
To assist with upgrades from 2.7, the previously documented deprecation of inspect.getfullargspec() has been reversed. This decision may be revisited again after the Python 2.7 branch is no longer officially supported.
Add new socket.TCP_CONGESTION (Linux 2.6.13) and socket.TCP_USER_TIMEOUT (Linux 2.6.37) constants. Patch written by Omar Sandoval.
Reading a corrupt config file left configparser in an invalid state. Original patch by Florian Höch.
Fix asyncio C Task to handle exceptions __traceback__.
PyUnicode_CompareWithASCIIString() now never raises exceptions.
The data model reference and the porting section in the What's New guide now cover the additional __classcell__ handling needed for custom metaclasses to fully support 487 and zero-argument super().
Fix python-gdb.py didn't support new dict implementation.