Code review comment for lp:~veebers/autopilot/fixing_backend_being_none

I've run the smoke image testing suite on my mako at home with this branch. I'm not sure if this is a problem or not. When run under our CI logic, I get a unity8 failure:

18:29:58.118 INFO globals:50 - Starting test unity8.indicators_client.tests.test_battery.TestDisplayMenus.test_brightness_slider (with touch)
18:29:58.119 WARNING testcase:118 - No tracing available - install the python-autopilot-trace package!
18:29:58.155 WARNING testcase:155 - Process manager backend unavailable, application snapshot support disabled.
18:29:58.227 INFO __init__:156 - Launching process: ['/usr/bin/indicators-client', '-testability', '-geometry', None]
18:29:58.272 ERROR testresult:35 - ERROR: unity8.indicators_client.tests.test_battery.TestDisplayMenus.test_brightness_slider(with touch)
18:29:58.274 ERROR testresult:35 - traceback: {{{
Traceback (most recent call last):
File "/home/phablet/autopilot/unity8/indicators_client/tests/test_battery.py", line 22, in setUp
super(TestDisplayMenus, self).setUp(self.geometry, self.grid_unit)
File "/home/phablet/autopilot/unity8/indicators_client/tests/__init__.py", line 57, in setUp
self.launch_test_local(geometry)
File "/home/phablet/autopilot/unity8/indicators_client/tests/__init__.py", line 62, in launch_test_local
"-geometry", geometry, app_type='qt')
File "/home/phablet/autopilot-override/autopilot/testcase.py", line 279, in launch_test_application
process = launch_application(launcher, app_path, *arguments, **kwargs)
File "/home/phablet/autopilot-override/autopilot/introspection/__init__.py", line 128, in launch_application
cwd=cwd
File "/home/phablet/autopilot-override/autopilot/introspection/__init__.py", line 167, in launch_process
**kwargs
File "/usr/lib/python2.7/subprocess.py", line 709, in __init__
errread, errwrite)
File "/usr/lib/python2.7/subprocess.py", line 1326, in _execute_child
raise child_exception
TypeError: execv() arg 2 must contain only strings
}}}

However, phablet-test-run is working. So i think its just something environmental at my place.