better comment

tracim/models/__init__.py

     # FIXME - G.M - 02-05-2018 - Check Zope/Sqlalchemy session conf.
     # We use both keep_session=True for zope and
     # expire_on_commit=False for sessionmaker to keep session alive after
-    # commit ( in order  to not have trouble like #52 or
-    # detached objects problems).
+    # commit ( in order  to not have trouble like
+    # https://github.com/tracim/tracim_backend/issues/52
+    # or detached objects problems).
     # These problem happened because we use "commit" in our current code.
     # Understand what those params really mean and check if it can cause
     # troubles somewhere else.
+    # see https://stackoverflow.com/questions/16152241/how-to-get-a-sqlalchemy-session-managed-by-zope-transaction-that-has-the-same-sc  # nopep8
     zope.sqlalchemy.register(
         dbsession,
         transaction_manager=transaction_manager,