Sækja Python 3.8 3.8.6

Core and Builtins
- bpo-41525: The output of python --help contains now only ASCII characters.
Library
- bpo-41817: fix tkinter.EventType Enum so all members are strings, and none are tuples
- bpo-41815: Fix SQLite3 segfault when backing up closed database. Patch contributed by Peter David McCormick.
- bpo-41517: fix bug allowing Enums to be extended via multiple inheritance
- bpo-39587: use the correct mix-in data type when constructing Enums
- bpo-41789: Honor object overrides in Enum class creation (specifically, __str__, __repr__, __format__, and __reduce_ex__).
- bpo-39651: Fix a race condition in the call_soon_threadsafe() method of asyncio.ProactorEventLoop: do nothing if the self-pipe socket has been closed.
- bpo-41720: Fixed turtle.Vec2D.__rmul__() for arguments which are not int or float.
- bpo-39728: fix default _missing_ so a duplicate ValueError is not set as the __context__ of the original ValueError
- bpo-37479: When Enum.__str__ is overridden in a derived class, the override will be used by Enum.__format__ regardless of whether mixin classes are present.
Documentation
- bpo-35293: Fix RemovedInSphinx40Warning when building the documentation. Patch by Dong-hee Na.
- bpo-37149: Change Shipman tkinter doc link from archive.org to TkDocs. (The doc has been removed from the NMT server.) The new link responds much faster and includes a short explanatory note.
Tests
- bpo-41731: Make test_cmd_line_script pass with option ‘-vv’.
Windows
- bpo-41744: Fixes automatic import of props file when using the Nuget package.
IDLE
- bpo-35764: Rewrite the Calltips doc section.
- bpo-40181: In calltips, stop reminding that ‘/’ marks the end of positional-only arguments.