I spend two hours to understand the problem.I didn't install git when i try to configure ssh access with private and public key for bitbucket.
Could you add proper message to page when user need to install git.
I got An internal error occurred during form field validation (HTTP 500). Please reload the page and if the problem persists, ask the administrator for help.
But it will be very cool when user see message " you need to install git from site"