python-flask-restful fails to build with Python 3.9.0a2.

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ERROR: Failure: ImportError (cannot import name 'Mapping' from 'collections' (/usr/lib64/python3.9/collections/__init__.py))
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Traceback (most recent call last):
  File "/usr/lib/python3.9/site-packages/nose/failure.py", line 39, in runTest
    raise self.exc_val.with_traceback(self.tb)
  File "/usr/lib/python3.9/site-packages/nose/loader.py", line 416, in loadTestsFromName
    module = self.importer.importFromPath(
  File "/usr/lib/python3.9/site-packages/nose/importer.py", line 47, in importFromPath
    return self.importFromDir(dir_path, fqname)
  File "/usr/lib/python3.9/site-packages/nose/importer.py", line 94, in importFromDir
    mod = load_module(part_fqname, fh, filename, desc)
  File "/usr/lib64/python3.9/imp.py", line 234, in load_module
    return load_source(name, filename, file)
  File "/usr/lib64/python3.9/imp.py", line 171, in load_source
    module = _load(spec)
  File "<frozen importlib._bootstrap>", line 702, in _load
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 786, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/builddir/build/BUILD/flask-restful-0.3.7/tests/test_reqparse.py", line 8, in <module>
    from flask_restful.reqparse import Argument, RequestParser, Namespace
  File "/builddir/build/BUILD/flask-restful-0.3.7/flask_restful/__init__.py", line 17, in <module>
    from collections import Mapping
ImportError: cannot import name 'Mapping' from 'collections' (/usr/lib64/python3.9/collections/__init__.py)
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See https://docs.python.org/3.9/whatsnew/3.9.html#removed

"The abstract base classes in collections.abc no longer are exposed in the regular collections module. This will help create a clearer distinction between the concrete classes and the abstract base classes."


For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.9/fedora-rawhide-x86_64/01161322-python-flask-restful/

For all our attempts to build python-flask-restful with Python 3.9, see:
https://copr.fedorainfracloud.org/coprs/g/python/python3.9/package/python-flask-restful/

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 3.9:
https://copr.fedorainfracloud.org/coprs/g/python/python3.9/

Let us know here if you have any questions.

Python 3.9 will be included in Fedora 33. To make that update smoother, we're building Fedora packages with early pre-releases of Python 3.9.
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.