image module depends on libcairo

[rgaudin]

Note sure what to do about it but the image module depends on a ffmpeg dependency of dependency (libcairo via libavcodec). This means that someone not planning on using any video related modules and thus not installing ffmpeg will see it fail (not at install stage but at import one)

[benoit74]

This is indeed something I noticed in warc2zim (see Dockerfile change in https://github.com/openzim/warc2zim/commit/217769e9f3169068273056fea4bd67ca007ce781#diff-dd2c0eb6ea5cfc6c4bd4eac30934e2d5746747af48fef6da689e85b752f39557L6) but forgot to mention here.

Should we simply mention libcairo in README dependencies?

[rgaudin]

I see it as good enough for now.

[benoit74]

Duplicate of https://github.com/openzim/python-scraperlib/issues/190