Question: Unable to update app: Error posting to URL: <https://appengine.google.com/api/appversion/create?app_id=ethereal-zodiac-803&version=1&>
409 Conflict
Another transaction by user suganya.karthik is already in progress for app: s~ethereal-zodiac-803, version: 1. That user can undo the transaction with "appcfg rollback".

See the deployment console for more details
Unable to update app: Error posting to URL: <https://appengine.google.com/api/appversion/create?app_id=ethereal-zodiac-803&version=1&>
409 Conflict
Another transaction by user suganya.karthik is already in progress for app: s~ethereal-zodiac-803, version: 1. That user can undo the transaction with "appcfg rollback".

Answer: 
Just as the message says, you need to use `rollback` command to undo the previous update that failed to complete. Just replace the word `update` with the word `rollback` (everything else stays the same) and run the command.

You can run it in the terminal window (command prompt) on your computer by running appcfg program.

* Python:
<https://cloud.google.com/appengine/docs/python/tools/uploadinganapp>
* Java: <https://cloud.google.com/appengine/docs/java/tools/uploadinganapp>
If anyone who has this issue is using Android Studio or Intellij, you can go to your Gradle/Maven tasks, click backend. and click Tasks, click google app engine, and click Rollback. instead of messing with the terminal.