I'm not sure what is the problem, but seems like full-text search is broken on
frontend when system default python-flaks-whooshee is installed, traceback:

    ...
    File "/copr/coprs_frontend/coprs/logic/coprs_logic.py", line 200, in get_multiple_fulltext
    query = query.whooshee_search(search_string, whoosheer=CoprWhoosheer)
    TypeError: whooshee_search() got an unexpected keyword argument 'whoosheer'

There's no arugment 'whoosheer', turns out there's probably copr-specific
python-flask-whooshee package:

    https://copr-be.cloud.fedoraproject.org/results/@copr/copr/fedora-24-x86_64/00395504-python-flask-whooshee/

Either we should use the system default pyhton-flask-whooshee package, or we
should package this into Fedora, too.  Also it is worth documenting in
copr-setup.txt properly.