qvm-kill: make error message more clear

See QubesOS/qubes-issues#5607.

qubesadmin/tests/tools/qvm_kill.py

@@ -64,3 +64,17 @@ class TC_00_qvm_kill(qubesadmin.tests.QubesTestCase):
             0)
         self.assertAllCalled()
 
+    def test_004_other_error(self):
+        self.app.expected_calls[
+            ('some-vm', 'admin.vm.Kill', None, None)] = \
+            b'2\x00QubesVMError\x00\x00Error message\x00'
+        self.app.expected_calls[
+            ('dom0', 'admin.vm.List', None, None)] = \
+            b'0\x00some-vm class=AppVM state=Running\n'
+        with qubesadmin.tests.tools.StderrBuffer() as stderr:
+            self.assertEqual(
+                qubesadmin.tools.qvm_kill.main(['some-vm'], app=self.app),
+                1)
+        self.assertAllCalled()
+        self.assertIn("Failed to kill 'some-vm': Error message",
+                      stderr.getvalue())

qubesadmin/tools/qvm_kill.py

@@ -45,7 +45,8 @@ def main(args=None, app=None):
             pass
         except (IOError, OSError, qubesadmin.exc.QubesException) as e:
             exit_code = 1
-            parser.print_error(str(e))
+            parser.print_error("Failed to kill '{}': {}".format(
+                domain.name, e))
 
     return exit_code