You need to put your API keys in a file, like the sample here: https://github.com/spacecowboy/NotePad/blob/master/core/assets/secretkeys.properties.sample
But first you will of course need to get yourself a key. Follow the instructions on this page: https://developers.google.com/google-apps/tasks/firstapp
Scroll to the section named Register your project.
And similar over here https://www.dropbox.com/developers/apps
Enter the full directory and call
gradle installDebug