D9578: Improve error message when parttest fails due to missing pdflatex

[Albert Astals Cid]

aacid accepted this revision.
This revision is now accepted and ready to land.

REPOSITORY
  R223 Okular

BRANCH
  master

REVISION DETAIL
  https://phabricator.kde.org/D9578

To: rkflx, aacid, #okular
Cc: #okular, michaelweghorn, gassaf, ngraham, aacid