Minecraft NOT launching on Max OSX launcher.

Put the summary of the bug you're having here

• Minecraft is not launching. It's only saying "Preparing"
  What I expected to happen was...:
  Describe what you thought should happen here

• Minecraft should launch...
  What actually happened was...:
  Describe what happened here

• Minecraft did NOT launch.
  Steps to Reproduce:
  1. Put a step by step guide on how to trigger the bug here
  2. ... - Open the Minecraft launcher. (On Mac OSX) and press 'Start'.
  3. ... - It's saying "Preparing Launch".