Use error code instead of error message

Author: eskombro

meilisearch/client.py

@@ -104,7 +104,7 @@ def get_or_create_index(self, uid, options=None):
         try:
             index.create(self.config, uid, options)
         except MeiliSearchApiError as err:
-            if err.message != 'index already exists':
+            if err.error_code != 'index_already_exists':
                 raise err
         return index