Can't Install PBE on Mac

I've successfully downloaded the PBE Client on my mac but when i try to copy it to my applications (or my desktop), an error pops up saying "The operation couldn't be completed because an unexpected error occurred (error code 101000)."

I can't get it to launch because the verifying process that happens when you install an app from the internet doesn't let me launch the client and I can't go in to bypass it if it's not an application for some dumb reason. Please help I want to play the reworked Shaco :)))