Python 3.9 is now generally available.

google.appengine.api.urlfetch.InvalidURLError

The URL given was empty or invalid.

Inherits From: Error, expected_type

Only HTTP and HTTPS URLs are allowed. The maximum URL length is 2048 characters. The login and password portion is not allowed. In deployed applications, only ports 80 and 443 for HTTP and HTTPS respectively are allowed.