I believe a bug was created, but there has been zero movement on it for over a year.
Where? Can you give a link? PDF export works fine for me and there are even automated tests to prove that PDF export works with every release of XWiki.
If you’re referring to Pdf export issue - #10 by mattyp and Loading... then there’s already a solution:
make sure that the user that is running xwiki has a home directory, because the pdf export creates a cache in ~/.fop
If that didn’t work for you then you should check the code of Apache FOP because the code that triggers your problem is not in XWiki, as shown by the stack trace you pasted
at org.apache.fop.fonts.FontCache.saveTo(FontCache.java:213)