distgit: extend the timeout limit for importing packages
    
    Imporing should be fast for the majority of packages. It is basically
    instant for packages with one or couple of sources. I am extending the
    timeout limit just because of texlive package which has ~6k
    sources.
    
    There is probably a space for improvement in the importing code so we
    shouldn't extend the timeout infinitely but rather rework the
    code. For the time being, increasing the timeout to three hours should
    be good enough.