[X] Adding cover art fails if there is an apostrophe in the directory path name

[DetlevD]

@DrTomBlinn

If I were typing in the path name, then I suppose I might be willing to learn to double-type any apostrophe in the path name. But I didn't type it in, Mp3tag filled it in for me, and then was unable to use what it filled in. That, in my opinion, is the bug. ...

There is no bug. Within the action "Import cover from file" Mp3tag supports the so called "format string", in order to provide scripting for the image filename (... look at the title of the edit field).
Therefore the Mp3tag Scripting Language needs some special characters to be escaped.
See also ...
/t/15384/1
How to save images as album arts according to audio filenames

DD.20151020.2352.CEST