Closes #91 + fix python None test

install/requirements.txt

 vobject==0.9.2
 waitress==0.8.9
 who-ldap==3.1.0
--e git+git@github.com:Nonolost/wsgidav.git@a5df223d5c66c252baa89ec5de8073f9f1494a8f#egg=wsgidav
+-e git+https://github.com/Nonolost/wsgidav.git@a5df223d5c66c252baa89ec5de8073f9f1494a8f#egg=wsgidav
 zope.interface==4.1.3
 zope.sqlalchemy==0.7.6
 

tracim/tracim/lib/auth/internal.py

         )).first()
 
         if user and user.validate_password(identity['password']):
-            if user.webdav_left_digest_response_hash == '':
+            if not user.webdav_left_digest_response_hash:
                 user.webdav_left_digest_response_hash = '%s:/:%s' % (identity['login'], identity['password'])
                 DBSession.flush()
                 # TODO : temporary fix to update DB, to remove