Fail assignment if child process failed to start
Deal with process transport not existing
Deal with processes being gone when killing them
Cosmetic: Add two empty lines for readability
Make checking for self.transport more explicit
Merge pull request #166 from guidow/handle_process_start_failure

Fail assignment if child process failed to start
Fix cleaning up assignments with no processes

Assignments that start zero processes would linger around forever in the
agent, eventually slowing stuff down by accumulating over time.  This
fixes that.

Some of our jobtypes will check if the desired output files already
exist, and forego starting any processes if they do.
Fix minor typo
Merge pull request #168 from guidow/fix_no_process_cleanup

Fix cleaning up assignments with no processes