_urllib_error_moved_attributes is a list with 3 elements: result of the call to the function MovedAttribute with 3 arguments:
_urllib_error_moved_attributes = [ MovedAttribute ( "URLError" , "urllib2" , "urllib.error" ) , MovedAttribute ( "HTTPError" , "urllib2" , "urllib.error" ) , MovedAttribute ( "ContentTooShortError" , "urllib" , "urllib.error" ) , ]