Google App Engine rollback

Unable to update app: Error posting to URL: https://appengine.google.com/api/appversion/create?app_id=xxxxx&version=1&
409 Conflict
Another transaction by user xxxxxx is already in progress for app: 
xxxxx, version: 1. That user can undo the transaction with "appcfg rollback".

If you get this error which is usually due to a previously interrupted deployment process

Navigate to your app engine sdk folder and then the bin folder.
Execute the command appcfg.sh rollback "Your application Path/war/WEB-INF"
You will need to supply your google email and password and this is the tricky part. If your login information is rejected, you need to go to your google account security settings and "enable for less secure apps", and try again.

error "No module named jinja2"

Building a google app on eclipse in python, I got this error.

First jinga2 comes bundled with Google App Engine for Python, so there's no need to go through the painful process of installing it on your machine.

To reference it from your project, add the following under the libraries section in your .yaml file

- name: jinja2
  version: latest

and import jinja2 in your code

IOError: [Errno 13] file not accessible:

Trying to build a google app on eclipse using python, I got this error while trying to render an html file.

To solve it, put the folder that contains the html in the same folder that contains the yaml file.

Google App Engine Launcher - NameError: global name 'execfile' is not defined (Python)

When trying to run the helloworld example, it shows this error:

NameError: global name 'execfile' is not defined

This happens when you have multiple versions of python on your system. The App Engine sets its default to python 3 although it already searched and found python 2.7 on the system before installation!!

Anyway, to solve it, go to Edit -> Preferences and change Python Path to refer to Python 2.7