The google.appengine.api.urlfetch package provides the following exception classes:

exception Error()

This is the base class for all exceptions in this package.

exception InvalidURLError()

The URL of the request was not a valid URL, or it used an unsupported method. Only http and https URLs are supported.

exception DeadlineExceededError()

The URL fetch timed out. More information is available in the App Engine article "Dealing with DeadlineExceededErrors".

exception DownloadError()

There was an error retrieving the data.

This exception is not raised if the server returns an HTTP error code: In that case, the response data comes back intact, including the error code.

exception ResponseTooLargeError()

The response data exceeded the maximum allowed size, and the allow_truncated parameter passed to fetch() was False.

exception SSLCertificateError()

The server did not have a valid SSL certificate, or the certificate was not signed by a trusted CA. This is only raised if the validate_certificate parameter passed to fetch() was True.