style(plausible): ruff format the rewritten event-tracking fixture

Self-inflicted: the rewrite in eecc4aa left the file unformatted, which the push
lint gate flags. Formatting only - no behaviour change.

(Note for the operator: the gate is red on main for unrelated reasons - 90 other
files also fail ruff format, and tests/unit/test_f211_sso_skip.py fails ruff
check C420. Neither is touched here; both predate this branch.)

tests/plausible/custom/test_event_tracking.py

@@ -110,7 +110,9 @@ def _register_site(domain: str, site: str) -> None:
         .replace("__SITE__", site)
     )
     out = lifecycle.exec_in_app(domain, ["/app/bin/plausible", "rpc", exs], service="app")
-    assert f"CCCI_SITE_OK {site}" in out, f"could not provision site {site!r} via the app: {out.strip()[-400:]}"
+    assert f"CCCI_SITE_OK {site}" in out, (
+        f"could not provision site {site!r} via the app: {out.strip()[-400:]}"
+    )
 
 
 def _post_event(base_domain: str, site: str, name: str, pathname: str) -> int:
@@ -142,9 +144,9 @@ def _ingest_and_count(
     last_status = None
     while True:
         last_status = _post_event(base_domain, site, name, pathname)
-        assert (
+        assert last_status == 202, (
-            last_status == 202
+            f"POST /api/event for {name!r} → HTTP {last_status} (expected 202)"
-        ), f"POST /api/event for {name!r} → HTTP {last_status} (expected 202)"
+        )
         time.sleep(interval)
         raw = _ch(base_domain, count_sql)
         count = int(raw) if raw.isdigit() else 0
@@ -192,6 +194,6 @@ def test_custom_event_roundtrip(live_app):
         live_app,
         f"SELECT name FROM events_v2 WHERE pathname = '{pathname}' LIMIT 1",
     )
-    assert (
+    assert stored_name == event_name, (
-        stored_name == event_name
+        f"custom event stored as {stored_name!r}, expected {event_name!r}"
-    ), f"custom event stored as {stored_name!r}, expected {event_name!r}"
+    )