Update dependency flake8-isort to v4

See merge request !31

Resolve "Register different import tasks/methods"

Closes #8

See merge request !29

Close #8

Fix lint issues and reformat

See merge request !26

Update dependency isort to v5

See merge request !27

Reason: UNTIS school years are always one full year
and school terms also can be a half year.

Update dependency mysqlclient to v2

See merge request !25

Delete no-longer existing lessons

See merge request !23

Use subject object to match course groups

See merge request !22

Fix paths to templates. Advances AlekSIS#246

See merge request !19

Update dependency flake8-black to ^0.2.0

See merge request !21

Enable testsuite and lint

See merge request !20