Calendar app didn't download but it giving Integrity Check Error


#1

I tried to add the Calendar app from the App Store and got an error. The app doesn't show as downloaded or enabled but is causing an integrity error. How can I remove whatever files are causing the error?


#2

The error is due to an invalid signature.


#3

I have followed the instructions in the blogpost below to get rid of the integrity check error:

https://owncloud.org/blog/good-bye-apps-owncloud-com/