Ignore pip warning in test_venv.test_with_venv().

Fix a warning on Windows 64-bit.

It's more to fix a conversion warning during compilation, I don't think that
Windows support current working directory larger than 2 GB ...

Issue #17758: Skip test_site if site.USER_SITE directory doesn't exist and
cannot be created.

On 32-bit system, only 4 bytes after dumped for the tail.

Pointers are formatted differently.

The first instruction of tracemalloc_add_trace() is traceback_new() which
already checks the GIL.

Issue #26558: If Py_FatalError() is called without the GIL, don't try to print
the current exception, nor try to flush stdout and stderr: only dump the
traceback of Python threads.

Issue #26516:

* Add PYTHONMALLOC environment variable to set the Python memory
  allocators and/or install debug hooks.
* PyMem_SetupDebugHooks() can now also be used on Python compiled in release
  mode.
* The PYTHONMALLOCSTATS environment variable can now also be used on Python
  compiled in release mode. It now has no effect if set to an empty string.
* In debug mode, debug hooks are now also installed on Python memory allocators
  when Python is configured without pymalloc.

in BaseHTTPRequestHandler

Initial patch by karlcow.

#25687: clarify that errors in tearDown increase the total number of reported errors.  Initial patch by HyeSoo Park.

Tamás Bence Gedai.

Tamás Bence Gedai.

Revert:
"Always test datetime.strftime("%4Y")

Issue #13305: Always test datetime.datetime.strftime("%4Y") for years < 1900."

In fact, strftime("%4Y") fails on most platforms.

Issue #13305: Always test datetime.datetime.strftime("%4Y") for years < 1900.

Patch by Dmitry Shachnev.

Issue #26323: Add assert_called() and assert_called_once() methods to
unittest.mock.Mock.

Patch by Dmitry Shachnev.

NotImplementedError instead of ImportError.