Restores the use of pyexpatns.h to isolate our embedded copy of the expat C
library so that its symbols do not conflict at link or dynamic loading time
with an embedding application or other extension modules with their own
version of libexpat.
5dc3f23b5f (diff-3afaf7274c90ce1b7405f75ad825f545) inadvertently removed it when upgrading expat.
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
```
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.
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.
