Bug#937396: pybtex: Python2 removal in sid/bullseye - reopen 937396

[Sandro Tosi]

Control: reopen -1

This bug was closed, but the package has still some dependencies towards
Python2 packages, in details:

(source:pybtex)Testsuite-Triggers->python-all
(source:pybtex)Testsuite-Triggers->python-nose
(source:pybtex)Testsuite-Triggers->python-pybtex

Re-opening, so that they can be taken care of.