According to the docs on App Engine, when using the appspot.com domain you have to do some trickery with -dot-
instead of .
in subdomains.
Please note that in April of 2013, Google stopped issuing SSL certificates for double-wildcard domains hosted at appspot.com (i.e. ..appspot.com). If you rely on such URLs for HTTPS access to your application, please change any application logic to use "-dot-" instead of ".". For example, to access version "1" of application "myapp" use "https://1-dot-myapp.appspot.com" instead of "https://1.myapp.appspot.com." If you continue to use "https://1.myapp.appspot.com" the certificate will not match, which will result in an error for any User-Agent that expects the URL and certificate to match exactly.
I am trying to figure out the best way to generate these URLs using the SDK without manually replacing the dots. I've tried modules.get_hostname(module="my module name")
but it returns a traditional sub-domain that triggers the SSL mismatch error.
Edit Per suggestion, I opened a feature request for this functionality