Fixes warnings in tests added in bpo-32117 and bpo-34603.

Flags SRE_FLAG_UNICODE and SRE_FLAG_ASCII are mutually exclusive.

The added functions are as below :

| os module     | Pathlib       |
| ------------- | ------------- |
| os.chmod   | Path.chmod  |
| os.mkdir  | Path.mkdir  | 
| os.rename | Path.rename |
| os.replace | Path.replace |
| os.rmdir  | Path.rmdir |
| os.remove, os.unlink | Path.unlink |
| os.path.samefile | Path.samefile |

Thanks


https://bugs.python.org/issue34825

This is needed to even the run the test suite on buildbots for affected platforms; e.g.:

```
./python.exe  ./Tools/scripts/run_tests.py -j 1 -u all -W --slowest --fail-env-changed --timeout=11700 -j2
/home/embray/src/python/test-worker/3.x.test-worker/build/python -u -W default -bb -E -W error::BytesWarning -m test -r -w -j 1 -u all -W --slowest --fail-env-changed --timeout=11700 -j2
Traceback (most recent call last):
  File "./Tools/scripts/run_tests.py", line 56, in <module>
    main(sys.argv[1:])
  File "./Tools/scripts/run_tests.py", line 52, in main
    os.execv(sys.executable, args)
PermissionError: [Errno 13] Permission denied
make: *** [Makefile:1073: buildbottest] Error 1
```

https://bugs.python.org/issue34871

`arg` is misspelled as `agr`. I noticed this when playing with https://bugs.python.org/issue34871


https://bugs.python.org/issue34871

Use tp_members and tp_getset instead.

Use tp_members and tp_getset instead.

The C implementation of asyncio.Task currently fails to perform the
cancellation cleanup correctly in the following scenario.

    async def task1():
        async def task2():
            await task3     # task3 is never cancelled

        asyncio.current_task().cancel()
        await asyncio.create_task(task2())

The actuall error is a hardcoded call to `future_cancel()` instead of
calling the `cancel()` method of a future-like object.

Thanks to Vladimir Matveev for noticing the code discrepancy and to
Yury Selivanov for coming up with a pathological scenario.

formatfloat() was not checking if PyBytes_FromStringAndSize()
failed, which could lead to a null pointer dereference in
_PyBytes_FormatEx().

Make it clear that the msg argument to assertWarns/assertWarnsRegex/assertRaisesRegex is keyword-only. (GH-9680)

A follow up to be4e5b89.

Fix a reference issue inside multiprocessing.Pool that caused the pool to remain alive if it was deleted without being closed or terminated explicitly.

Fixes broken build on OpenBSD-current.

closes bpo-34868: Improve error message with '_' is combined with an invalid type specifier. (GH-9666)

property_descr_get() uses a "cached" tuple to optimize function
calls. But this tuple can be discovered in debug mode with
sys.getobjects(). Remove the optimization, it's not really worth it
and it causes 3 different crashes last years.

Microbenchmark:

./python -m perf timeit -v \
    -s "from collections import namedtuple; P = namedtuple('P', 'x y'); p = P(1, 2)" \
    --duplicate 1024 "p.x"

Result:

Mean +- std dev: [ref] 32.8 ns +- 0.8 ns -> [patch] 40.4 ns +- 1.3 ns: 1.23x slower (+23%)

Patch by Serhiy Storchaka (in PR #9642).

* Compiling a string annotation containing a lambda with keyword-only
argument without default value caused a crash.

* Remove the final "*" (it is incorrect syntax) in the representation of
lambda without *args and keyword-only arguments when compile from AST.

* Improve the representation of lambda without arguments.

The waiting is pretty normal for any asyncio program, logging its time just adds
a noise to logs without any useful information provided.



https://bugs.python.org/issue34849

Switch "list" with "iterable" to match with the implementation.

Support for threadless builds was removed in a6a4dc81.

_pickle.Unpickler.__init__() should return -1 if Pdata_New() fails, not 1.

Since ProactorEventLoop is now the default in 3.8, remove examples
using it explicitly on Windows.





https://bugs.python.org/issue34687

After some failures in AMD64 FreeBSD CURRENT Debug 3.x buildbots
regarding tests in test_multiprocessing_spawn and after examining
similar failures in test_socket, some errors in the calculation of
ancillary data buffers were found in multiprocessing.reduction.

CMSG_LEN() can often be used as the buffer size for recvmsg() to
receive a single item of ancillary data, but RFC 3542 requires portable
applications to use CMSG_SPACE() and thus include space for padding,
even when the item will be the last in the buffer.

The failures we experience are due to the usage of CMSG_LEN() instead of
CMSG_SPACE().

Improvements:
1. Include the number of valid data characters in the error message.
2. Mention "number of data characters" rather than "length".


https://bugs.python.org/issue34736

Report the filename to the exception when raising {gdbm,dbm.ndbm}.error in
dbm.gnu.open() and dbm.ndbm.open() functions, so it gets printed when the
exception is raised, and can also be obtained by the filename attribute of the
exception object.