Ladok3

What's Changed
* Fixes more parts to check for empty passwd and usernames by dbosk in https://github.com/dbosk/ladok3/pull/81


**Full Changelog**: https://github.com/dbosk/ladok3/compare/v4.11...v4.12

What's Changed
* `keyring` doesn't raise exceptions, but returns `None` by dbosk in https://github.com/dbosk/ladok3/pull/80


**Full Changelog**: https://github.com/dbosk/ladok3/compare/v4.10...v4.11

What's Changed
* Update README by dbosk in https://github.com/dbosk/ladok3/pull/79
* Bugfix: Handle missing grading scales by dbosk in https://github.com/dbosk/ladok3/pull/69


**Full Changelog**: https://github.com/dbosk/ladok3/compare/v4.9...v4.10

Bumps cryptography version

**Full Changelog**: https://github.com/dbosk/ladok3/compare/v4.7...v4.9

Bumps depends' versions

**Full Changelog**: https://github.com/dbosk/ladok3/compare/v4.6...v4.7

Improves error handling when there are no credentials

**Full Changelog**: https://github.com/dbosk/ladok3/compare/v4.5...v4.6