* hacky string coercion to fix bug in cli datasource export (#7728)

superset/models/helpers.py

@@ -244,7 +244,7 @@ class ImportMixin(object):
                         )
                         for child in getattr(self, c)
                     ],
-                    key=lambda k: sorted(k.items()),
+                    key=lambda k: sorted(str(k.items())),
                 )
 
         return dict_rep