monitor_dbus_signals: check variant_level equality

Signed-off-by: mulhern <amulhern@redhat.com>

Author: mulkieran

scripts/monitor_dbus_signals.py

@@ -110,6 +110,33 @@ def __repr__(self):
         )
 
 
+class DifferentVariantLevel(Diff):  # pylint: disable=too-few-public-methods
+    """
+    Represents a case where the property value is correct but the variant
+    level does not match. The variant levels among the GetManagedObjects
+    result, the Properties.GetAll result and the PropertiesChangedSignal
+    result should always be the same, because both are encoded using dicts,
+    and the values of the dicts are always defined as variant types, since
+    they must be heterogeneous.
+    """
+
+    def __init__(
+        self, object_path, interface_name, key, old_value, new_value
+    ):  # pylint: disable=too-many-positional-arguments,too-many-arguments
+        self.object_path = object_path
+        self.interface_name = interface_name
+        self.key = key
+        self.old_value = old_value
+        self.new_value = new_value
+
+    def __repr__(self):
+        return (
+            f"DifferentVariantLevel({self.object_path!r}, "
+            f"{self.interface_name!r}, {self.key!r}, {self.old_value!r}, "
+            f"{self.new_value!r})"
+        )
+
+
 class NotInvalidatedProperty(Diff):  # pylint: disable=too-few-public-methods
     """
     Represents a case where the property should have been invalidated but
@@ -692,6 +719,14 @@ def _check_props(object_path, ifn, old_props, new_props):
                         ChangedProperty(object_path, ifn, key, old_value, new_value)
                     )
 
+            if (
+                old_value is not INVALIDATED
+                and new_value.variant_level != old_value.variant_level
+            ):
+                diffs.append(
+                    DifferentVariantLevel(object_path, ifn, key, old_value, new_value)
+                )
+
         return diffs
 
     def _check():