Administrator(s) of a Review Board instance are given the option to
automatically associate the instance's SSH key with new/existing
repositories, if supported by the hosting service, from the Repository 
form. 

Manually ensured key association completed under the conditions required
for existing repositories:
   - created new repository using hosting service that supports SSH key 
     association (GitHub)
   - after repository created, edited repository, checking associate 
     SSH key form field.
   - confirmed key uploaded to GitHub

Manually ensured key association completed under the following conditions 
for new repositories:
   - from the admin, added new repository, using GitHub as the hosting 
     service, and setting the "Associate SSH key" field.
   - confirmed key uploaded to GitHub

Manually confirmed that correct error message returned when key 
association failed. Confirmed that key association not attempted when 
the form already contained errors.