Bugfix

This commit fixes the problem with the new version of pymongo and flask-login as well as a bug in the holomorphic modular forms. 
Also, if you have a local mongo database make sure that each database has a user  with name 'lmfdb' and password 'readonly'. If not you should add this user (with the option read_only=True).
Everything works for me with the fixes in this branch with sage 5.10 (in 5.11 there are new problems with the holomorphic modular forms)