I tried:
rm ~/.appcfg_oauth2_tokens
Whole process with page authentication finish successfully for both accounts (owner role) with same result
appcfg.py update --no_cookies
Same result
appcfg.py update --noauth_local_webserver
Token is displayed, accepted in terminal, process continues towards same result.
I also tried to add another google account as owner, with same result. When I mistype application name, error is different, so I guess this is not a problem. Goapp deploy and appcfg seems to be same tool basically, both have same results in the end.
Any ideas?
Try checking the appengine-web file at /webapp/WEB-INF sounds like you have a reserved application name or application+version
Edit: For further consultation I am adding the conclusion of the thread.
Deploying from the GCP console was a valid workaround to the issue.
https://cloud.google.com/sdk/gcloud/reference/app/create
https://cloud.google.com/appengine/docs/python/tools/uploadinganapp
Hint from Nilo_DS was pointing in right direction. Using gcloud commands, I was able to upload app correctly. Still not sure what is going on when using goapp command, but this workaround is good enough for me. Commands I used were
gcloud init
gcloud beta app create
gcloud deploy