'"is" with a literal. Did you mean "=="?' Python warning in zip.py
*This bug was originally reported by Boyuan Yang (byang@debian.org) in Debian bug [#945531](https://bugs.debian.org/945531):*
```
Package: diffoscope
Severity: minor
Version: 132
-> % LC_ALL=3DC sudo dpkg-reconfigure diffoscope
/usr/lib/python3/dist-packages/diffoscope/comparators/zip.py:88:
SyntaxWarning: "is" with a literal. Did you mean "=3D=3D"?
return 0 if returncode is 3 else returncode
-> % diffoscope --version
diffoscope 132
Please consider suppressing this warning in the next release.
issue