fix(logs): failures name their job, VM and user; the new VM form shows a list it could not load

- A failed cancel hook logged "worker task cancel failed": it now names
  the job, its kind, resource and user, with the traceback for a fault
  of the panel.
- novncd logged "Console connection failed" without the VM or the user.
- django-axes wrote four INFO lines a login ("Reset 0 access
  attempts"...); logins are on the Logs page, so it logs warnings only.
- The new VM form's machine types and disk buses answered 200 with an
  empty object when libvirt failed, and nothing was logged: the list
  stayed empty, the form could not go on and said nothing. They answer
  400 with the error, as the pool's volume list does, the warning is
  logged with the compute, and the form's lists show an error they get
  with the page's messages.

computes/tests/test_cpu_graph.py

@@ -71,7 +71,7 @@ class GraphTestCase(TestCase):
         self.assertEqual((data["cpudata"], data["memdata"]["total"]), (None, None))
         self.assertNotIn("cpu_sample", data)
 
-    def test_a_host_that_cannot_be_connected_to_answers_without_values(self):
+    def test_a_host_that_cannot_be_connected_to_answers_without_values_or_with_its_error(self):
         down = ConnectionFailed("192.0.2.1 is down")
         with patch("computes.views.wvmHostDetails", side_effect=down), patch(
             "computes.models.wvmHostDetails", side_effect=down
@@ -79,7 +79,9 @@ class GraphTestCase(TestCase):
             self.assertIsNone(self.graph()["cpudata"])
             for url in (reverse("machines", args=[self.compute.id, "x86_64"]),
                         reverse("buses", args=[self.compute.id, "x86_64", "q35", "disk"])):
-                self.assertEqual(json.loads(self.client.get(url).content), {})
+                # a list the new VM form waits for: the error, not an empty answer
+                response = self.client.get(url)
+                self.assertEqual((response.status_code, json.loads(response.content)), (400, {"error": "192.0.2.1 is down"}))
 
 
 @unittest.skipUnless(shutil.which("node"), "node is not installed")

computes/tests/test_views.py

@@ -5,6 +5,7 @@ from django.contrib.auth import get_user_model
 from django.core.exceptions import ObjectDoesNotExist
 from django.shortcuts import reverse
 from django.test import TestCase
+from libvirt import libvirtError
 
 from vrtManager.connection import CONN_SOCKET, connection_manager
 from computes.models import Compute
@@ -190,6 +191,17 @@ class ComputesTestCase(TestCase):
         )
         self.assertEqual(response.status_code, 200)
 
+    def test_a_list_the_host_does_not_give_is_an_error_not_an_empty_list(self):
+        # the new VM form showed nothing and could not go on; the error was nowhere
+        for url, method in ((reverse("machines", args=[self.compute.id, "x86_64"]), "get_machine_types"),
+                            (reverse("buses", args=[self.compute.id, "x86_64", "q35", "disk"]), "get_disk_device_types")):
+            with self.subTest(method), patch("computes.models.wvmHostDetails") as conn, \
+                    self.assertLogs("computes.views", "WARNING") as logs:
+                getattr(conn.return_value, method).side_effect = libvirtError("Cannot recv data")
+                response = self.client.get(url)
+            self.assertEqual((response.status_code, json.loads(response.content)), (400, {"error": "Cannot recv data"}))
+            self.assertIn(f"of compute {self.compute.name} failed: Cannot recv data", logs.output[0])
+
     def test_a_disk_is_offered_the_hosts_disk_buses(self):
         with patch("computes.models.wvmHostDetails") as conn:
             conn.return_value.get_disk_device_types.return_value = ["disk", "cdrom", "lun"]