small refactors

backend/tracim_backend/lib/core/user.py

         )
         return user
 
-    def _check_email(self, email) -> bool:
+    def _check_email(self, email: str) -> bool:
         """
         Check if email is completely ok to be used in user db table
         """
         """
         Verify if given email does not already exist in db
         """
-        return self._session.query(User.email).filter(User.email==email).all() != []  # nopep8
+        return self._session.query(User.email).filter(User.email==email).count() != 0  # nopep8
 
     def _check_email_correctness(self, email: str) -> bool:
         """

backend/tracim_backend/models/context_models.py

             email_notification: bool = True,
     ) -> None:
         self.email = email
+        # INFO - G.M - 2018-08-16 - cleartext password, default value
+        # is auto-generated.
         self.password = password or password_generator()
         self.public_name = public_name or None
         self.timezone = timezone or ''