The Bitbucket configuration experience confuses some users. Since

Bitbucket moved to a standardized Atlassian e-mail-based system for

logging in, people often try to use their e-mail addresses to link up

with the account. However, with Bitbucket, the API actually expects a

Bitbucket username, and providing an e-mail address ends up triggering

an unexpected HTTP error code, which we weren't handling.
On top of this, users who had two-factor authentication could not log

in with their standard password, which confused some users. This was

made worse by the fact that Bitbucket provides no reasonable error in

this case. Users need to use app-specific passwords, which wasn't

obvious, and is buried in a document somewhere on the Bitbucket support

portal.
We now provide a custom authentication form, which gives useful

instructions on authenticating, spelling out exactly what's needed for

both the username and password.
One additional improvement has to do with adding other users'

repositories. We previously only offered support for adding your linked

user's repository or a team repository. We now offer an option for

choosing another user. That takes care of some customer confusion we've

had in the past.

Tested the Other User option manually.
Tested with two-factor auth enabled and using both app passwords (which

work) and standard Bitbucket passwords (which do not, and fail gracefully

now).
Checked the help output for the different choices.
Unit tests pass.