update test dependencies
remove unused variable detected by pyflakes
upgrade Aspen to 0.36

fixes #2984 and #3004
actually, remove the entire function, we don't use it anymore
don't consider suspicious users as ANON (fixes #2786)
Merge pull request #3019 from gratipay/aspen-0.36

Upgrade Aspen to 0.36
Merge pull request #3021 from gratipay/suspicious-not-anon

Allow suspicious users to log in
Merge pull request #3017 from gratipay/update-test-deps

Update test dependencies
Bump version to 1749
drop the `is_locked` column
fix tests
remove obsolete comment
removed unused variable