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After creating google service account with permission as shown below - deployment fails with message . I am failing to understand where this is going wrong.
====
$ gcloud iam service-accounts get-iam-policy cdemail#appid.iam.gserviceaccount.com
bindings:
- members:
- serviceAccount:cdemail#appid.iam.gserviceaccount.com
role: roles/owner
etag: Bxxxxxxxxg=
====
$ gcloud auth activate-service-account --key-file ../a.json
Activated service account credentials for: [cdemail#appid.iam.gserviceaccount.com]
$ gcloud app deploy
ERROR: (gcloud.app.deploy) You do not have permission to access app [appid].

Have got it working now.
$ gcloud app deploy --log-http --verbosity=debug
reason on why it fails is seen with action to enable app engine api (link will be shown in command output). Enable the api - then try deploying again (this time without --log-http as this is resulting in a gcloud crash).
It should go through.

To add to npr's answer. Run this in the command if you have not authenticated yourself for your default app/project (after enabling the API):
gcloud auth application-default login