It was common for people to put invalid repository names or usernames

into the Bitbucket repository config form. When this happened, we'd

either end up storing bad account information, fail with a cryptic

error, or crash.
Some of the most common problems here have been fixed.
We now check the the validity of the username and password prior to

storage. We fetch the user session API, using the credentials provided

by the user. The credential data is only stored if this succeeds.
If any API request results in an HTTP 401, we raise an

AuthorizationError. All other errors result in a HostingServiceError

(previously, we'd raise an Exception, which wouldn't always be caught

correctly). If the data from the server was a valid error payload, we

now parse that and display the error message.
Repositories are now validated properly as well. A repository name that

looks like a path (has a '/') or contains '.git' will immediately result

in an error instructing the user to provide just the name. If a name

meets the criteria, but is not found, a suitable error will also be

shown instead of a JSON payload.

Tested each failure condition manually.
Tested successful authentication and repository access.
Unit tests pass.