Not the op, but that only worked half of the time when running install scripts from the internet. To make it really work you basically had to setup and maintain a full bash environment in parallel to the fish environment (env variables, paths, etc...). Most software packages out there really expect that you're running in a bash-compatible environment.
I launch a bash shell, which inherits parent fish shell's env, then run the command and exit back to fish.
All my scripts have "#!/usr/bin/env bash" at the top but in some cases that didn't help. Also, I think some bash specific bits in my .bashrc had syntax errors. Eventually I just didn't want to deal with the hassle of switching over.