bibclassify: error handling and PEP8 fixes

Signed-off-by: Georgios Papoutsakis <georgios.papoutsakis@cern.ch>
workflows: bibclassify task fix

* Also fixes PEP8 issues in hodlingpen.py.

Signed-off-by: Georgios Papoutsakis <georgios.papoutsakis@cern.ch>