Run autopep8 as well as clang-format when calling "make format",
the PATHS argument is passed to both utilities which will only operate on files they support.
For example: `make format PATHS=release/scripts` formats Python scripts, `make format PATHS=source/blender/blenlib` would format C/C++.
If users really want they can format C/C++ & Python files at the same time since both formatting utilities filter on file extension.
`make format PATHS="release/scripts/startup/nodeitems_builtins.py source/creator/creator.c"`
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NOTE: I wasn't able to use the Python binary in place (it gives an error that `libcrypt.so.1` isn't found), and didn't think it necessary to use the pre-compiled Python. So `PYTHON` will always be used to execute `autopep8.py` found in our `../lib/` directory.