[Reproducible-builds] Bug#815844: diffoscope won't build without python-magic from PyPi

[Leo Famulari]

Source: diffoscope

Dear Maintainer,

I am maintaining the diffoscope package in GNU Guix [0].

I recently updated from version 34 to 49, and found that I could not
build diffoscope from source without the python-magic package from PyPi
[1].

However, diffoscope's README [2] says that:

``Magic-file-extension`` can be used instead of
``python-magic``. It is built from `file
<http://www.darwinsys.com/file/>`_.
Available on Debian and Fedora as ``python3-magic``.

I removed the requirement of python-magic from setup.py and built
against the Python bindings distributed with `file`, as packaged in Guix
[3]. Diffoscope seems to work just fine this way.

I even confirmed, with strace, that diffoscope was using libmagic from
`file`.

Will you consider making python-magic an optional dependency of
diffoscope, so that downstream packagers don't have to package
python-magic from PyPi or work around this issue by patching setup.py?

[0]
https://www.gnu.org/software/guix/package-list.html#diffoscope

[1]
https://pypi.python.org/pypi/python-magic/

[2]
https://anonscm.debian.org/cgit/reproducible/diffoscope.git/tree/README.rst#n58

[3]
https://www.gnu.org/software/guix/package-list.html#python-file