libxml2 fails to build with Python 3.10.0a1.

make[2]: Leaving directory '/builddir/build/BUILD/libxml2-2.9.10/py3/python/tests'
test.xml:1: parser error : Couldn't find end of Start Tag foo
<foo
    ^
SystemError: PY_SSIZE_T_CLEAN macro must be defined for '#' formats

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/builddir/build/BUILD/libxml2-2.9.10/py3/python/tests/../../../python/tests/push.py", line 9, in <module>
    ctxt.parseChunk("/>", 2, 1)
  File "/builddir/build/BUILD/libxml2-2.9.10/python/libxml2.py", line 5101, in parseChunk
    ret = libxml2mod.xmlParseChunk(self._o, chunk, size, terminate)
SystemError: <built-in function xmlParseChunk> returned a result with an error set

For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.10/fedora-rawhide-x86_64/01715877-libxml2/

For all our attempts to build libxml2 with Python 3.10, see:
https://copr.fedorainfracloud.org/coprs/g/python/python3.10/package/libxml2/

Testing and mass rebuild of packages is happening in copr. You can follow these instructions to test locally in mock if your package builds with Python 3.10:
https://copr.fedorainfracloud.org/coprs/g/python/python3.10/

Let us know here if you have any questions.

Python 3.10 will be included in Fedora 35. To make that update smoother, we're building Fedora packages with early pre-releases of Python 3.10.
A build failure prevents us from testing all dependent packages (transitive [Build]Requires), so if this package is required a lot, it's important for us to get it fixed soon.
We'd appreciate help from the people who know this package best, but if you don't want to work on this now, let us know so we can try to work around it on our side.