Fix detection of error messages. (#843)

* Fix detection of error messages.

Don't try to do exact matches, but use "in".
One issue being that the message usually looks like:
  '"No registered event listener."'
(Note the extra quotes.)

* client.py: Remove outer quotes from error messages

pyoverkiz/client.py

@@ -809,7 +809,7 @@ async def check_response(response: ClientResponse) -> None:
             ) from error
 
         if result.get("errorCode"):
-            message = result.get("error")
+            message = result.get("error").strip("'")
 
             # {"errorCode": "AUTHENTICATION_ERROR",
             # "error": "Too many requests, try again later : login with xxx@xxx.tld"}