Tighten caught exception type in prepare_build_user
Move user setup out of exception handler in prepare_build_user
Simplify prepare_build_user by using subprocess.check_call
Make sure that usual /sbin directories are in /bin:/usr/bin:/home/jcorbin/bin:/home/jcorbin/.local/bin
Merge remote-tracking branch 'jcorbin/master' into jcorbin