zsh: no matches found: celery[redis]

I met this error message when installing celery\[redis\]

    $ sudo pip install -U celery[redis]
    zsh: no matches found: celery[redis]

This is because [zsh uses square brackets to pattern-match](http://zsh.sourceforge.net/Guide/zshguide05.html).

Therefore,

    $ sudo pip install -U "celery[redis]"

instead of 

    $ sudo pip install -U celery[redis]

might be better.