We already overwrite it in ERP5Type/Utils.py, then _showwarning method from PyPDF2 breaks ERP5
PyPDF2 can not overwrite _showwarning, because we already did it.
I tried to extend test.erp5.testERP5PDFMerge to reproduce this issue, but I can not catch it in unit test. Any idea?
/cc @romain, @vpelletier