What do you mean with running App Engine locally? There used to be a local development server, but that did not survive the 2to3 transition. GCP does ship a Datastore and a PubSub emulator, but no Cloud Storage for example (someone wrote this one [1], which sort-of works but it does not behave 1:1 like GCS, so ironically my tests have to work around bugs in the emulator...).
[1] https://github.com/oittaa/gcp-storage-emulator