tpircher-zz
Update MutableMapping import for Python 3.10
The ABCs were moved to collections.abc in Python 3.3, but aliases were in the collections module to avoid breaking code. Python 3.10 removed those aliases.
The Travis config in the repo declares compatibility with Python 3.2, which does not have collections.abc. I don't know if this package still runs on 3.2, and virtualenv doesn't support 3.2 (according to its docs, I didn't try), so I couldn't test it on 3.2. On the assumption that no one cares about 3.2 anymore, this commit does not catch ImportError and fall back to the old import.
Unfortunately I have been locked out from the GitHub account; the fix is now applied to the new repository in https://github.com/tpircher/pycrc
