Strange search results for 'pypy' (BB-8873)

This is likely a wider issue, but manifests itself pretty well when trying to search for 'pypy'. Steps to reproduce

1. Open bitbucket.org, click on owner/repository search box in the title bar
2. Type 'pyp' (attached screenshot pyp.png). In this case search produces fairly reasonable matches, correctly including some with 'pypy' in it.
3. Type 'pypy' (attached screenshot pypy.png). In this case, search results don't include pypy at all. Expected result is that those repositories (including the main one at pypy/pypy) should show up right at the top of the list.