[firedrake] firedrake-install on macOS Sierra

Dear all, I am installing firedrake on my new laptop from scratch (running macOS Sierra). The installation script runs and installs virtualenv, up to the point where I get this: Virtual env installed. Please run firedrake-install again. But when I run python firedrake-install again, it just does the same thing (similar to the previous step) and does not install firedrake (and petsc etc..). What shall I do? Best, Anna.