Replace UserWarning with AuthenticationError

This is a more accurate error for what is actually happening and lets us
save the actual response in case the user wants to do something with it.

pyracing/client.py

@@ -10,6 +10,7 @@
     session_data,
     upcoming_events,
 )
+from .exceptions.authentication_error import AuthenticationError
 
 from datetime import datetime
 import httpx
@@ -61,7 +62,7 @@ async def _authenticate(self):
                 'indicating an authentication failure. If credentials are '
                 'correct, check that a captcha is not required by manually '
                 'visiting members.iracing.com')
-            raise UserWarning(auth_response.read())
+            raise AuthenticationError('Login Failed', auth_response)
         else:
             logger.info('Login successful')