python2.7 cannot be opened because of a problem
Was fighting with this issue today, after I upgraded python using brew, the annoying pop up wouldn't let me work on my Mac! The only difference is that it was shouting for python3.4. After couple hours of digging I just decided to:


remove all python3 whatsoever, the one installed by brew and the one installed manually from dmg.
search for all remaining symlinks to python I've had on my development projects folder. After deactivating all the venv's and removing the symlinks the pop up was gone.


Then I found this post of jeremycade which explains the less aggressive approach.