Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/apport/report.py", line 197, in _run_hook
    symb['add_info'](report, ui)
  File "/usr/share/apport/package-hooks/upstart.py", line 171, in add_info
    if os.path.exists(system_state_file) or os.path.exists(session_state_file):
  File "/usr/lib/python3.3/genericpath.py", line 18, in exists
    os.stat(path)
TypeError: can't specify None for path argument