Comment 10 for bug 912558

I think we now understand what is happening here. Essentially, the problem occurs when jobs refer to binaries that don't exist on the system. The common case of this scenario is if you've installed a package with a job file in /etc/init/, but then removed the package. The binaries have now been removed, but the configuration files remain (unless you 'purge' the package).

The specific scenario causing the failure is if Upstart attempts to run a single-line *non-existent* command with no shell meta-characters in it, the assertion fires.