PEP 394[1] says,
"In cases where the script is expected to be executed outside virtual
environments, developers will need to be aware of the following
discrepancies across platforms and installation methods:
* Older Linux distributions will provide a python command that refers
to Python 2, and will likely not provide a python2 command.
* Some newer Linux distributions will provide a python command that
refers to Python 3.
* Some Linux distributions will not provide a python command at all by
default, but will provide a python3 command by default."
Debian has forced the issue by choosing the third option[2]:
"NOTE: Debian testing (bullseye) has removed the "python" package and
the '/usr/bin/python' symlink due to the deprecation of Python 2."
Switch our shebang from "#!/usr/bin/env python" to "#!/usr/bin/env
python3" in some places. Remove some 2/3 version checks if we know we're
running under Python 3. Remove the "coding: utf-8" in a bunch of places
since that's the default in Python 3.
[1]https://www.python.org/dev/peps/pep-0394/#for-python-script-publishers
[2]https://wiki.debian.org/Python
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