* Replace "try/finally: os.remove()" with self.addCleanup(support.unlink) or
  self.addCleanup(support.rmdir): the support function handles the case when
  the file doesn't exist
* Replace "try/finally: f.close()" with "with open(...) as f:"
* test_getsize: add a second test with a different size
* Create file using "x" mode to ensure that the file didn't exist before, to
  detect bugs in tests
* Open files in unbuffered mode (buferring=0) to write immediatly data on disk
* Replace map() with simpler code
* Split isdir() unit test into two units tests to make them less dependant,
  same change for isfile() test
* test_samefile(): test also two different files

Issue #25911:

* Try to fix test_os.BytesWalkTests on Windows
* Try to mimick better the reference os.DirEntry on Windows
* _DummyDirEntry now caches os.stat() result
* _DummyDirEntry constructor now tries to get os.stat()

* Update code for the name regrtest output format.
* Enhance also test_regrtest test on --fromfile

Issue #25911: Use support.check_warnings() to expect or ignore
DeprecationWarning in test_os.

Issue #26588: Optimize memory footprint of _tracemalloc before non-zero domain
is used. Start with compact key (Py_uintptr_t) and also switch to pointer_t key
when the first memory block with a non-zero domain is tracked.

On Windows, socket.setsockopt() raises an OverflowError if the socket option is
larger than INT_MAX bytes.

Issue #18787: restore "bin" name in test_spwd but catch KeyError.

Ignore empty lines in stderr.

Issue #18787: try to get the "root" entry which should exist on all UNIX
instead of "bin" which doesn't exist on OpenIndiana.

We know that Py_SIZE(b) is -1 or 1 an so fits into the sdigit type.

Don't check if the dict key exists before getting the key. Instead get the key
and handle error.

Restore the previous code for stack_overflow().

Issue #23848, #26622:

* faulthandler now only logs fatal Windows exceptions.
* write error code as decimal, not as hexadecimal
* replace "Windows exception" with "Windows fatal exception"

Only display duration if a test takes more than 30 seconds.

wcsnlen_s() result type is size_t.

Don't return a void value.

Issue #23848: On Windows, faulthandler.enable() now also installs an exception
handler to dump the traceback of all Python threads on any Windows exception,
not only on UNIX signals (SIGSEGV, SIGFPE, SIGABRT).

This function will be reused by faulthandler.

Issue #26588:

* Pass the hash table rather than the key size to hash and compare functions
* _Py_HASHTABLE_READ_KEY() and _Py_HASHTABLE_ENTRY_READ_KEY() macros now expect
  the hash table as the first parameter, rather than the key size
* tracemalloc_get_traces_fill(): use _Py_HASHTABLE_ENTRY_READ_DATA() rather
  than pointer dereference
* Remove the _Py_HASHTABLE_ENTRY_WRITE_PKEY() macro
* Move "PKEY" and "PDATA" macros inside hashtable.c

* Optimize tracemalloc_add_trace(): modify hashtable entry data (trace) if the
  memory block is already tracked, rather than trying to remove the old trace
  and then add a new trace.
* Add _Py_HASHTABLE_ENTRY_WRITE_DATA() macro

* _Py_HASHTABLE_ENTRY_DATA: change type from "char *" to "const void *"
* Add _Py_HASHTABLE_ENTRY_WRITE_PKEY() macro
* Rename _Py_HASHTABLE_ENTRY_WRITE_DATA() macro to
  _Py_HASHTABLE_ENTRY_WRITE_PDATA()
* Add _Py_HASHTABLE_ENTRY_WRITE_DATA() macro

No need to remove the old trace if the memory block didn't move.