Identify two possible sources of error better

Signed-off-by: mulhern <[email protected]>

Author: mulkieran

src/stratis_cli/_error_reporting.py

@@ -182,11 +182,25 @@ def _interpret_errors_1(
     # generated code is constructed, or if the introspection data from
     # which the auto-generated code is constructed does not match the
     # daemon interface. This situation is unlikely and difficult to
-    # elicit in a test.
+    # elicit in a test. It may arise however, in the case where there
+    # is an error producing a property and that property, even although
+    # part of the official API, is missing from the GetManagedObjects result.
     if isinstance(
         error,
         (DbusClientMissingSearchPropertiesError, DbusClientMissingPropertyError),
     ):  # pragma: no cover
+        if len(errors) > 1:
+            maybe_key_error = errors[1]
+            if isinstance(maybe_key_error, KeyError):
+                return (
+                    f'Property "{maybe_key_error.args}" belonging to '
+                    f'interface "{error.interface_name}" is not in this '
+                    "GetManagedObjects result. This could be due to the fact "
+                    "that stratisd omitted the property from the "
+                    "GetManagedObjects result because there was an error in "
+                    "obtaining that value."
+                )
+
         return _DBUS_INTERFACE_MSG
 
     if isinstance(error, StratisCliEngineError):
@@ -246,7 +260,7 @@ def _interpret_errors_1(
     return None  # pragma: no cover
 
 
-def _interpret_errors_2(errors):
+def _interpret_errors_2(errors):  # pylint: disable=too-many-return-statements
     """
     Interpret the error when it is known that the first error is a
     DPClientInvocationError
@@ -309,6 +323,16 @@ def _interpret_errors_2(errors):
                         f"{next_error.get_dbus_message()}."
                     )
 
+                if isinstance(context, DPClientGetPropertyContext):  # pragma: no cover
+                    return (
+                        f"stratisd failed to perform the operation that you "
+                        f"requested, because it could not get the D-Bus "
+                        f'property "{context.property_name}" belonging to '
+                        f'interface "{error.interface_name}". '
+                        f"It returned the following error: "
+                        f"{next_error.get_dbus_message()}."
+                    )
+
             if next_error.get_dbus_name() == "org.freedesktop.DBus.Error.NoReply":
                 context = error.context
                 if (