I have been working on a very benign Android application for a couple months now and all of a sudden I started getting this message on my device when I try to re-install it from IntelliJ.
My question is, what sort of things would cause Android OS to display this message? If I were to ever release this app, I certainly would not want my users to have to see this before installing.
I had the same problem and it was caused by gradle plugin v2.2.0 (beta version and also RC). When I changed the version back to 2.1.3 problem dissapeared.