👌 IMPROVE: Warning message for group with no entry point

closes #3919

aiida/orm/groups.py

@@ -50,12 +50,13 @@ def __new__(cls, name, bases, namespace, **kwargs):
         from aiida.plugins.entry_point import get_entry_point_from_class
 
         newcls = ABCMeta.__new__(cls, name, bases, namespace, **kwargs)  # pylint: disable=too-many-function-args
-
-        entry_point_group, entry_point = get_entry_point_from_class(namespace['__module__'], name)
+
+        mod = namespace['__module__']
+        entry_point_group, entry_point = get_entry_point_from_class(mod, name)
 
         if entry_point_group is None or entry_point_group != 'aiida.groups':
             newcls._type_string = None
-            message = f'no registered entry point for `{name}` so its instances will not be storable.'
+            message = f'no registered entry point for `{mod}:{name}` so its instances will not be storable.'
             warnings.warn(message)  # pylint: disable=no-member
         else:
             newcls._type_string = entry_point.name  # pylint: disable=protected-access