Hello, I have a MacPro 2009 - Siera OS 10.12.5. I am trying to install Python 3.6.5 but no joy. I tried opening in Finder (open. open with) but it keeps saying “python-3.6.5-macosx10.9.pkg” is damaged and can’t be opened. You should move it to the Trash." only option is to cancel or move to trash. what do I have to do to install? I Googled, and all videos show just click and run the installer. but it won't do it on my machine. Any idea? Sorry if it had been asked but I can't replicate what they say. It just won't let me pass the above message. Do I need to run something called Homebrew?