To resolute Gatekeeper issues on MacOS Sierra we prepared a script to automatically unlock images and programs (annoying image/application is damaged messages pretending you cannot open things).

In cases you prefer a manual installation the image file in this folder could be used. For that reason you might have to partially or completely disable Gatekeeper checks.

Option I
For a certain application run in Terminal:
sudo xattr -rd com.apple.quarantine /Applications/LockedApp.app

Option II
To disable checks globally run in Terminal:
sudo spctl --master-disable