Fix warning for migration (#1592)

pay-api/migrations/versions/b6e28faea978_rename_tables_to_plurals.py

@@ -136,7 +136,7 @@ def _rename_sequence(m, new_table_name, table):
     if id_column is not None and id_column.server_default is not None:
         seq = id_column.server_default.arg.text
         # format is 'nextval(\'org_id_seq\'::regclass)'
-        seq_name = re.search("nextval\(\'(.*)\'::regclass", seq).group(1)
+        seq_name = re.search(r"nextval\(\'(.*)\'::regclass", seq).group(1)
         new_seq_name = seq_name.replace(table, new_table_name, 1)
         if seq_name != new_seq_name:
             print(f'\t<<<<<<<<<Renaming PK : {seq_name} to {new_seq_name} of table {table}')