* BPO-27639: Correct return type for UserList slicing operation

Added logic to __getitem__ magic method for UserList to ensure that the return
type matches that of self.

https://bugs.python.org/issue36801

When the future returned by shield is cancelled, its completion callback of the
inner future is not removed. This makes the callback list of inner inner future
grow each time a shield is created and cancelled.

This change unregisters the callback from the inner future when the outer
future is cancelled.



https://bugs.python.org/issue35125

(lint cleanup) This import causes an argument parameter to shadow the global import name.

*Moved from python/asyncio#493.*

This PR fixes issue python/asyncio#480, as explained in [this comment](https://github.com/python/asyncio/issues/480#issuecomment-278703828).

The `_SelectorDatagramTransport.sendto` method has to be modified ~~so `_sock.sendto` is used in all cases (because it is tricky to reliably tell if the socket is connected or not). Could that be an issue for connected sockets?~~ *EDIT* ... so `_sock.send` is used only if `_sock` is connected.

It also protects `socket.getsockname` against `OSError` in `_SelectorTransport`. This might happen on Windows if the socket is not connected (e.g. for UDP broadcasting).


https://bugs.python.org/issue31922

Used **spookylukey**'s patch from 2011-01-24



https://bugs.python.org/issue11001

Instead of attempting to acquire and release them all across fork
which was leading to deadlocks in some applications that had chained
their own handlers while holding multiple locks.

bpo-36783: Added C API Documentation for Time_FromTimeAndFold and PyDateTime_FromDateAndTimeAndFold (GH-13147)

Python 3.8.0a4

unittest.mock.mock_open() results now respects the argument of read([size])
Co-Authored-By: remilapeyre <remi.lapeyre@henki.fr>

Modern Linux distros such as Debian Buster have default OpenSSL system
configurations that reject connections to servers with weak certificates
by default.  This causes our test suite run with external networking
resources enabled to skip these tests when they encounter such a failure.

Fixing the network servers is a separate issue.

Classes that define __str__ the same as __repr__ can
just inherit it from object.

In addition, fix some other minor violations of C99.

* Doc/c-api/exceptions.rst: fix grammar

skip issue
skip news

* Use ", in that case"
Co-Authored-By: blueyed <github@thequod.de>

Added two keyword arguments, `delay` and `interleave`, to
`BaseEventLoop.create_connection`. Happy eyeballs is activated if
`delay` is specified.

We now have documentation for the new arguments. `staggered_race()` is in its own module, but not exported to the main asyncio package.


https://bugs.python.org/issue33530

_osx_support and copyreg are not imported from site on macOS for now.