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.

console/novncd

@@ -25,6 +25,7 @@ from websockify import ProxyRequestHandler, WebSocketProxy  # noqa: E402
 from console.sshtunnels import open_tunnel, tunnel_target  # noqa: E402
 from console.tokens import ACCESS_CHECK, authorize, may_still_open, session_user_id  # noqa: E402
 from logs.audit import write  # noqa: E402
+from operations.utils import safe_text, traceback_of  # noqa: E402
 from vrtManager.connection import CONN_SOCKET, CONN_SSH, CONNECT_TIMEOUT  # noqa: E402
 from vrtManager.util import is_loopback  # noqa: E402
 from webvirtcloud.settings import WS_HOST, WS_PORT  # noqa: E402
@@ -120,7 +121,7 @@ class ConsoleClient:
             logging.warning("Console connection without a token in its websocket URL")
             return
 
-        user = None
+        instance = user = None
         try:
             instance, user = authorize(token, "vnc")
             # a token read from a log or a URL is no use without its user's session
@@ -133,7 +134,9 @@ class ConsoleClient:
             write(user.username if user else "", "-", "", f"VNC console refused: {e}", False, address)
             return
         except Exception as e:
-            logging.warning("Console connection failed: %s", e)
+            # the VM and its user, as the refusal above; a fault of the panel with its traceback, without secrets
+            logging.warning("Console connection to VM %s for %s failed: %s%s", instance.name if instance else "-",
+                            user.username if user else "-", safe_text(e), traceback_of(e))
             return
         logging.debug(
             "Console of %s@%s (type %s): %s:%s, socket %s",