datajoint/table.py: add 'see allow_direct_insert to direct_insert error message

Author: Chris Turner

datajoint/table.py

@@ -170,7 +170,7 @@ def insert(self, rows, replace=False, skip_duplicates=False, ignore_extra_fields
         # prohibit direct inserts into auto-populated tables
         if not (allow_direct_insert or getattr(self, '_allow_insert', True)):  # _allow_insert is only present in AutoPopulate
             raise DataJointError(
-                'Auto-populate tables can only be inserted into from their make methods during populate calls.')
+                'Auto-populate tables can only be inserted into from their make methods during populate calls. (see allow_direct_insert)')
 
         heading = self.heading
         if inspect.isclass(rows) and issubclass(rows, QueryExpression):   # instantiate if a class