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- Add support for Python 3.9.
- Drop support for Python 3.5 and 2.7.
- Fix a bug where the encoding of Python files was not determined in the
same way as by Python itself. See `issue 15
<https://github.com/mgedmin/findimports/issues/15>`_. This requires
the use of ``tokenize.open`` which is not in Python 2.7.