Hello Guix!

Since we updated imlib2 to version 1.6 the feh test suite was failing,
however it looks harmless. The output expectation just needs tweaking a
little.

I've reported it upstream https://github.com/derf/feh/issues/497 but in
the meantime, here's a patch for downstream! I don't think such a patch
is suitable upstream as it would mean the tests would fail on previous
versions of imlib2.