Thanks to Shaun Walbridge for noticing.

It can be seen on various buildbots like 3.x.cea-indiana-amd64
and 3.x.murray-snowleopard:

/export/home/buildbot/64bits/3.x.cea-indiana-amd64/build/Modules/_ssl.c:2227: warning: unused variable 'libver'

/Users/buildbot/buildarea/3.x.murray-snowleopard/build/Modules/_ssl.c:2227: warning: unused variable ‘libver’

NOTE: A direct call of super.__init__ is not endorsed!

syscall() function requires #include <unistd.h>.

Issue #26735: Fix os.urandom() on Solaris 11.3 and newer when reading more than
1,024 bytes: call getrandom() multiple times with a limit of 1024 bytes per
call.

Patch written by Demur Rumed.

Based on patch by Xiang Zhang.

Reported by Robert on docs@p.o.

The default value of __len__ is 0, not 1:

    >>> from unittest.mock import MagicMock
    >>> mock = MagicMock()
    >>> len(mock)
    0

Reported by Alex on docs@p.o.

Remove the remaining VMSError reference. VMS support is gone.

in places where Py_DECREF was used.

error handler for stdin and stdout.

Remove redundant tests now that str is unicode.

This eliminates a few redundant test cases.

* No longer attempts to close already freed socket file descriptor
* Use socket object to be compatible with Windows
* Do not use a timeout to avoid complication with non-blocking mode
* Use internal localhost server rather than depending on a third party
* Avoid trouble with buffered HTTP data by testing tunnelled CONNECT data

Issue #26716. IOError is a deprecated alias to OSError since Python 3.3.

Patch by Giampaolo Rodola'.

Patch by Geoff Wilson.

ByteArrayAsStringTest.fixtype() was converting test data to bytes, not byte-
array, therefore many of the test cases inherited in this class were not
actually being run on the bytearray type.

The tests in buffer_tests.py were redundant with methods in string_tests
.MixinStrUnicodeUserStringTest and string_tests.CommonTest. These methods are
now moved into string_tests.BaseTest, where they will also get run for bytes
and bytearray.

This change also moves test_additional_split(), test_additional_rsplit(), and
test_strip() from CommonTest to BaseTest, meaning these tests are now run for
bytes and bytearray. I plan to eliminate redundancies with existing tests in
test_bytes.py soon.

This syncs to rev 7b43ada77821d23e55e3a4b35f6055a59b9e1ad7 there.

Summary:

- Add typing.DefaultDict (as a generic variant of collections.defaultdict).

- Use collections.Reversible if it exists (only relevant for Python 3.6).

- Revamped generic class behavior to conform to updated PEP 484.

- Improve speed of Generic.__new__.

- Make sure __init__ is called for new Generic instances. Fix issue #26391.

- Refactor async support to be compatible with 3.2, 3.3, 3.4.

- Remove 'io' and 're' from __all__ (they still exist, just not
  included by "import *"). Fix issue #26234.

- Change @overload -- you can now use it outside stubs (you still
  cannot call the decorated function though).