Pull request reviewers typeahead for private repositories shows all Bitbucket users

Steps to repro

1. Create a new pull request in a private repository
2. Type a character in the "Reviewers" field

Expected result

A list of people with access to the private repository (and therefore the contents of the pull request) partially matching the character.

Actual result

A list of all Bitbucket usernames partially matching the character, with some arbitrary ranking that includes people with repository access. Adding any of the other people shows "

does not have access to view this pull request" in red error text.