controllers/user.py: edit_form: errors as a list

This is more flexible to add new errors.
3 jobs for feature-s/test-mod-passwd in 6 minutes and 37 seconds (queued for 2 minutes and 52 seconds)
Status Job ID Name Coverage
  Test Tools
passed #416484
test_tools

00:00:07

 
  Test Unit
passed #416485
web
test_server_unit

00:00:17

 
  Test Functional
passed #416486
x86_64 docker
test_server_functional

00:06:12