Currently the script uses ImageMagick library. But the SVG conversion
is handled unreliably. ImageMagick has various backends to do it and
some of them don't work. I saw this problem many times, and is now
affecting my system. A more reliable conversion can be achieved using
`rsvg-convert`. Isn't as good as InkScape, but is smaller and works
well.
In the process I'm trimming the extra blank space generated by
PcbDraw when we have objects in layers like "User Drawings" that
extends beyond the PCB size.
I'm also compressing JPGs more aggressively, this makes a real
difference between PNG and JPG outputs. Otherwise the difference
is too small.
This is mainly to allow successful tests on CI/CD where we are running
as root. In practice is also a good idea to respect the permissions.
In real life installers make them r/w.
Files using macros can't be cached. Now if we find caches for them we
try to delete the caches (pypi installation for example). If we can't
remove the files a warning is generated.
If we fail to load a plug-in an error explaining it is generated.
Also added a test to reproduce it.
Salvador E. Tropea