praw-dev/praw — pull request #133 by Damgaard (2012-10-19 12:29:27+00:00)
Title: (un)hide and is_username_available

Reddit raises an exception if a username submitted is invalid and returns false if it is already taken. This difference can also be seen on the web-end when trying to create a new account. I've folded it into one, so both taken and invalid usernames give the result False and no errors is raised. This should simplify things for any client program trying to test whether a new redditor can be created with that name.

There are more explanations on the why and the what in the commit messages.