Either grab the following fonts manually:

* [FiraSans.sty](http://ctan.math.washington.edu/tex-archive/fonts/fira/latex/FiraSans.sty)
* [FiraMono.sty](http://ctan.math.washington.edu/tex-archive/fonts/fira/latex/FiraMono.sty)
* [mwieghts.sty](http://mirror.aarnet.edu.au/pub/CTAN/macros/latex/contrib/mweights/mweights.sty)

or ```sudo apt install texlive-fonts-extra```