The documentation within the tsearch2 backend labels it as being
experimental and that it should not be used. The have_backend() function
in roundup.backend returns False indicating that it does not exist and
is labeled as "currently not working". The PostgreSQL website also seems
to indicate that it has been deprecated since v8.3 when text searching
was integrated into the core[1].

Considering all this, it seems like the best option is to just remove
the tsearch2 backend.

[1] http://www.postgresql.org/docs/9.4/static/tsearch2.html