tests: fix tests against latest dependency versions

13 jobs for 51-disable-mail-notifications-for-specific-user in 18 minutes and 11 seconds (queued for 3 seconds)
Status Name Job ID Coverage
  Test
passed py3.5-min-mysql #28716

00:09:32

passed py3.5-min-postgresql #28714

00:18:01

passed py3.5-min-sqlite #28712

00:09:07

passed py3.5-pypi-mysql #28717

00:10:14

95.0%
passed py3.5-pypi-postgresql #28715

00:09:50

95.0%
passed py3.5-pypi-sqlite #28713

00:09:16

94.0%
passed py3.6-min-mysql #28722

00:09:55

passed py3.6-min-postgresql #28720

00:18:09

passed py3.6-min-sqlite #28718

00:08:57

passed py3.6-pypi-mysql #28723

00:10:19

95.0%
passed py3.6-pypi-postgresql #28721

00:09:39

95.0%
passed py3.6-pypi-sqlite #28719

00:09:18

94.0%
passed test-docs #28724

00:04:08