bug#43151: Resolve Calibre run-time dependency

[Brendan Tildesley]

There is actually a Bug report by Andreas for this very issue. I created 
a bug report just for updating, and fixed this issue after it while I 
could, without realising. Sorry for all the confusion with things 
happening in 3 different threads.

I created an updated patch just for this one here. 
https://issues.guix.gnu.org/43151#5

Your patch also works I think but it will wrap the programs twice, so 
you will get calibre, .calibre-real, and ..calibre-real-real, etc for 
every program, which seems ugly. My patch reproduces the same PYTHONPATH 
that is set in python-build-system in addition to wrapping PYTHONPATH 
(unless I made a mistake), although at the cost of code duplication. I 
leave it to you and who ever is reviewing this to decide which way is 
more correct and push one, haha.


Please continue any discussion of the QtWebEngine bug on issue 43121: 
43151@debbugs.gnu.org / https://issues.guix.gnu.org/43151