Add regression test for #6320

distributed/cli/tests/test_dask_worker.py

@@ -682,3 +682,23 @@ def dask_setup(worker):
         await c.wait_for_workers(1)
         [foo] = (await c.run(lambda dask_worker: dask_worker.foo)).values()
         assert foo == "setup"
+
+
+@pytest.mark.parametrize("nanny", ["--nanny", "--no-nanny"])
+def test_error_during_startup(monkeypatch, nanny):
+    # see https://github.com/dask/distributed/issues/6320
+    scheduler_port = 8786
+    scheduler_addr = f"tcp://127.0.0.1:{scheduler_port}"
+
+    monkeypatch.setenv("DASK_SCHEDULER_ADDRESS", scheduler_addr)
+    with popen(["dask-scheduler"]):
+        with popen(
+            [
+                "dask-worker",
+                scheduler_addr,
+                nanny,
+                "--worker-port",
+                str(scheduler_port),
+            ],
+        ) as worker:
+            assert worker.wait(5) == 1