tests/conftest: Don't subclass dbusmock.DBusTestCase

For historical reasons, dbusmock is written for Python's unittest
framework and most of what it does is done via @classmethod. We called
it on the subclassed object though, so we got some weird behaviors.

In particular, things like `a = foo.someval` would resolve to the
parent class' `someval` but `foo.someval = a` would set that value on
the subclassed object. This lead, indirectly, to our forked dbus-daemon
not getting terminated.

This needs to be be fixed in dbusmock (see [1]) but for now simply work
around this by instantiating the DBusTestCase class directly.

[1] martinpitt/python-dbusmock#184

tests/conftest.py

@@ -11,27 +11,17 @@
 from tests import PortalMock
 
 
-class SessionBusMock(dbusmock.DBusTestCase):
- def __init__(self):
- super().__init__()
- self._dbus_con = None
-
- @property
- def dbus_con(self) -> "dbus.Bus":
- return self._dbus_con
-
-
 @pytest.fixture()
-def session_bus() -> Iterator[SessionBusMock]:
+def session_bus() -> Iterator[dbusmock.DBusTestCase]:
  """
  Fixture to yield a DBusTestCase with a started session bus.
  """
- bus = SessionBusMock()
+ bus = dbusmock.DBusTestCase()
  bus.setUp()
  bus.start_session_bus()
  con = bus.get_dbus(system_bus=False)
  assert con
- bus._dbus_con = con
+ setattr(bus, "dbus_con", con)
  yield bus
  bus.tearDown()
  bus.tearDownClass()