[bugfix] site_tests.TestAlldeletedrevisionsAsUser fails
[bugfix] site_tests.TestAlldeletedrevisionsAsUser fails

This test only passed when the test user lacked any deleted revisions. This
both corrects that and provides more helpful output in the case of failures.

Bug: T287393
Change-Id: I5c04d8bc928472ceb15fc0f58130c2c20cabcff0

wikimedia/pywikibot-core,wikimedia/pywikibot-core