Issue #26603:

* Implement finalizer for os.scandir() iterator
* Set the source parameter when emitting the ResourceWarning warning
* Close the iterator before emitting the warning

Issue #26604:

* Add a new optional source parameter to _warnings.warn() and warnings.warn()
* Modify asyncore, asyncio and _pyio modules to set the source parameter when
  logging a ResourceWarning warning

Add parenthesis.

Issue #26588: Enhance assertion in set_reentrant()

Issue #26588: Fix _tracemalloc start/stop: don't play with the reentrant flag.

set_reentrant(1) fails with an assertion error if tracemalloc_init() is called
first in a thread A and tracemalloc_start() is called second in a thread B. The
tracemalloc is imported in a thread A. Importing the module calls
tracemalloc_init(). tracemalloc.start() is called in a thread B.

So it's possible to get debug messages in test_tracemalloc.

Issue #26588.

Try to debug random failure on buildbots.

Timestamps should help to debug slow buildbots, and timeout and hang on
buildbots.

Issue #26530:

* Add C functions _PyTraceMalloc_Track() and _PyTraceMalloc_Untrack() to track
  memory blocks using the tracemalloc module.
* Add _PyTraceMalloc_GetTraceback() to get the traceback of an object.

Issue #26588:

* The _tracemalloc now supports tracing memory allocations of multiple address
  spaces (domains).
* Add domain parameter to tracemalloc_add_trace() and
  tracemalloc_remove_trace().
* tracemalloc_add_trace() now starts by removing the previous trace, if any.
* _tracemalloc._get_traces() now returns a list of (domain, size,
  traceback_frames): the domain is new.
* Add tracemalloc.DomainFilter
* tracemalloc.Filter: add an optional domain parameter to the constructor and a
  domain attribute
* Sublte change: use Py_uintptr_t rather than void* in the traces key.
* Add tracemalloc_config.use_domain, currently hardcoded to 1

Issue #26588: Remove _Py_hashtable_delete() from hashtable.h since the function
is not used. Keep the C code in hashtable.c as commented code if someone needs
it later.

Issue #26588: Remove copy_data, free_data and get_data_size callbacks from
hashtable.h. These callbacks are not used in Python and makes the code more
complex.

Remove also the _Py_HASHTABLE_ENTRY_DATA_AS_VOID_P() macro which uses an unsafe
pointer dereference (can cause memory alignment issue). Replace the macro usage
with _Py_HASHTABLE_ENTRY_READ_DATA() which is implemented with the safe
memcpy() function.

Issue #26588: hashtable.h now supports keys of any size, not only
sizeof(void*). It allows to support key larger than sizeof(void*), but also to
use less memory for key smaller than sizeof(void*).

uuid.uuid4() always uses os.urandom() after 756d040aa8e8.

Patch by jgauthier.

Patch by Andrew Szeto.

Without the patch, line 1010 of Lib/datetime.py wasn't covered
by the test suite.

Patch by Colin Williams.

casting iobase_finalize to destructor is not needed

Issue #26590: support.check_warnings() stores warnins, but ResourceWarning now
comes with a reference to the socket object which indirectly keeps the socket
alive.

Issue #26590: Implement a safe finalizer for the _socket.socket type. It now
releases the GIL to close the socket. Use PyErr_ResourceWarning() to raise the
ResourceWarning to pass the socket object to the warning logger, to get the
traceback where the socket was created (allocated).