The warning is provided on an open Google app launcher

I am newbie. I have successfully installed Google App Engine Launcher. I followed closely every step that is given here https://askubuntu.com/questions/308534/google-app-engine-gui-launcher-for-ubuntu-13-04

when i tried to open google app launcher i got the following warning

$ ./GoogleAppEngineLauncher.py
WARNING:root:
  Warning: Prerequisites for App Engine development are missing!

  A valid python binary must be available.  In addition,
  the App Engine SDK must be installed.  Here are the current
  values we found:

    python = /usr/bin/python
    App Engine SDK root = None

  Please install the missing pieces and restart the launcher.
  If these are installed but the Launcher failed to find them,
  you can configure their location by editing Launcher preferences.

  The Launcher preferences can be modified by selecting Edit > Preferences.

      

        
        
        
      

    

Please note that I have already installed the Google App Engine SDK for python.

I tried to change the preference in google app engine launcher, but I can't hit "change". A good app launcher doesn't work.

I don’t understand what is going wrong here? Please help me fix this warning.