* Issue #25234: Skip test_eintr.test_open() under OS X to avoid hanging
* Issue #25868: Try to make test_eintr.test_sigwaitinfo() more reliable
  especially on slow buildbots. Use a pipe to synchronize the parent and the
  child processes.

Issue #26227: On Windows, getnameinfo(), gethostbyaddr() and gethostbyname_ex()
functions of the socket module now decode the hostname from the ANSI code page
rather than UTF-8.

Also add some more tests. Based on patch by Sye van der Veen.

Most of the docs has already been updated in c3c188a0325a.

Most of the docs has already been updated in c3c188a0325a.

Patch by Raphael Das Gupta.

Patch by Raphael Das Gupta.

Augment htest to include all major IOBinding functions.

Issue #26217: resize_compact() must set wstr_length to 0 after freeing the wstr
string. Otherwise, an assertion fails in _PyUnicode_CheckConsistency().

Mention the name of the invalid type in error message of AST validation for
constants.

Suggestion made by Joseph Jevnik on a review.

obj2ast_constant() code is baesd on obj2ast_object() which has a special case
for Py_None. But in practice, we don't need to have a special case for
constants.

Issue noticed by Joseph Jevnik on a review.

Issue #26146.

Remove unnecessary test case comment in urllib.parse.py. These are asserted as test cases.

Issue #26146: Add a new kind of AST node: ast.Constant. It can be used by
external AST optimizers, but the compiler does not emit directly such node.

An optimizer can replace the following AST nodes with ast.Constant:

* ast.NameConstant: None, False, True
* ast.Num: int, float, complex
* ast.Str: str
* ast.Bytes: bytes
* ast.Tuple if items are constants too: tuple
* frozenset

Update code to accept ast.Constant instead of ast.Num and/or ast.Str:

* compiler
* docstrings
* ast.literal_eval()
* Tools/parser/unparse.py

and better generated code (on both GCC and CLang).

and for better code generation.

* Add comment to the maxlen structure entry about the meaning of maxlen == -1
* Factor-out code common to deque_append(left) and deque_extend(left)
* Factor inner-loop in deque_clear() to use only 1 test per loop instead of 2
* Tighten inner-loops for deque_item() and deque_ass_item() so that the
  compiler can combine the decrement and test into a single step.

* Write one import per line
* Sort imports by name
* Add an empty line: 2 empty lines between code blocks at the module level (PEP 8)

with no known parent package.

Previously SystemError was raised if the parent package didn't exist
(e.g., __package__ was set to '').
Thanks to Florent Xicluna and Yongzhi Pan for reporting the issue.