python-bottle fails to build with Python 3.9.0a2.

+ /usr/bin/python3 setup.py build '--executable=/usr/bin/python3 -s'
Traceback (most recent call last):
  File "/builddir/build/BUILD/bottle-0.12.13/setup.py", line 10, in <module>
    import bottle
  File "/builddir/build/BUILD/bottle-0.12.13/bottle.py", line 86, in <module>
    from collections import MutableMapping as DictMixin
ImportError: cannot import name 'MutableMapping' from 'collections' (/usr/lib64/python3.9/collections/__init__.py)


The abcs can now only be imported from collections.abc.

For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.9/fedora-rawhide-x86_64/01139224-python-bottle/

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

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, but the initial bootstrapping has already started.
A build failure this early in the bootstrap sequence blocks us very much.