Make sure STDOUT and STDERR are correctly handled

[fauust]

When generating the PDF, the following seems to go to STDERR:

[INFO] 08:10:03 Started
[INFO] 08:10:03 Generating en(2689)
[INFO] 08:11:16 Merging HTML
[INFO] 08:14:53 Starting wk
[INFO] 08:56:14 Wrote PDF to output_en/MariaDBServerKnowledgeBase.pdf
[INFO] 08:57:32 Merging HTML
[INFO] 08:59:51 Starting wk
[INFO] 09:39:53 Wrote PDF to output_en/MariaDBServerKnowledgeBase.pdf
[INFO] 09:39:53 Finished

This should not be the case.

[fauust]

see: https://docs.python.org/3/howto/logging-cookbook.html#custom-handling-of-levels