controllers/user.py, models/db.py: Define password_min_length for users

As users will be able to modify their own password, we need to give a limit on the minimal password length
Status Job ID Name Coverage
  Test Tools
passed #181220
test_tools

00:00:09

 
  Test Unit
failed #200141
web
test_server_unit

00:00:20

failed #181221
web
test_server_unit

00:00:24

 
  Test Functional
skipped #181222
docker x86_64
test_server_functional
 
Name Stage Failure
failed
test_server_unit Test Unit
Makefile:40: recipe for target 'unit_server' failed
make: *** [unit_server] Error 2
make: Entering directory '/home/gitlab-runner/builds/b8d876c1/0/vidjil/vidjil/server'
pkill -f fuse_server.py
make: Leaving directory '/home/gitlab-runner/builds/b8d876c1/0/vidjil/vidjil/server'
Uploading artifacts...
server/web2py/test-reports/TEST*xml: found 16 matching files
Uploading artifacts to coordinator... ok id=200141 responseStatus=201 Created token=VyCzTE5h
ERROR: Job failed: exit status 1