Hi Simon, I've made some fixes to hopefully avoid confusion about this in the future (admittedly it was a really bad error message).
Better sanity checking for the tor command... https://gitweb.torproject.org/stem.git/commitdiff/e22a753058a2b9c61301c62e2d...
Reporting testing as having failed if tor can't start... https://gitweb.torproject.org/stem.git/commitdiff/bf2f7f2a461b535ddd21728e29...
Thanks for the catches! -Damian