Bug#1088717: fontmake: FTBFS: E assert ['', ...] == ['', ...]

[s3v]

Dear Maintainer,

After applying this commit [1], I was able to build your package in a
sid chroot environment (amd64 arch).

Kind Regards

[1] https://github.com/googlefonts/fontmake/commit/ca96d25faa67638930