- Prefer instance attributes over local variables - the former ones do
not leak into traceback object and are cleaned up by tests framework.
- Use 'with' syntax for handling files.
- Use subprocess.DEVNULL instead of open('/dev/null') where applicable
- Delete local variables when not needed anymore.
- improve TestPool mock - init_volume now return appropriate mock type,
instead of TestPool
- improve patching base directory (/var/lib/qubes) - it is stored in
more than one place...
- fix inheritance in TC_01_ThinPool class
- fix expected LVM volume names ('vm-' prefix)
- fix cleanup after FilePool tests - remove temporary qubes.xml
- asyncio usage
- better reporting in integ.storage - include error message in the
report, not only as a comment in code
Changed the inheritance hierarchy:
1. Renamed `SystemTestsMixin` to `SystemTestCase`
2. `SystemTestCase` is a child of `QubesTestCase`
3. All classes extending the prior `SystemTestsMixin` now just extend `object`
