The test failed on branch=master, cloud=gce:
test artifacts and logs in: artifacts/acceptance/version-upgrade/run_1
	versionupgrade.go:296,versionupgrade.go:471,versionupgrade.go:453,versionupgrade.go:200,versionupgrade.go:188,acceptance.go:63,acceptance.go:104,test_runner.go:768: dial tcp 127.0.0.1:26261: connect: connection refused

	cluster.go:1667,context.go:140,cluster.go:1656,test_runner.go:849: dead node detection: /go/src/github.com/cockroachdb/cockroach/bin/roachprod monitor local --oneshot --ignore-empty-nodes: exit status 1 3: dead
		2: 23562
		1: 23903
		4: 23677
		Error: UNCLASSIFIED_PROBLEM: 3: dead
		(1) UNCLASSIFIED_PROBLEM
		Wraps: (2) attached stack trace
		  -- stack trace:
		  | main.glob..func14
		  | 	/go/src/github.com/cockroachdb/cockroach/pkg/cmd/roachprod/main.go:1147
		  | main.wrap.func1
		  | 	/go/src/github.com/cockroachdb/cockroach/pkg/cmd/roachprod/main.go:271
		  | github.com/spf13/cobra.(*Command).execute
		  | 	/go/src/github.com/cockroachdb/cockroach/vendor/github.com/spf13/cobra/command.go:830
		  | github.com/spf13/cobra.(*Command).ExecuteC
		  | 	/go/src/github.com/cockroachdb/cockroach/vendor/github.com/spf13/cobra/command.go:914
		  | github.com/spf13/cobra.(*Command).Execute
		  | 	/go/src/github.com/cockroachdb/cockroach/vendor/github.com/spf13/cobra/command.go:864
		  | main.main
		  | 	/go/src/github.com/cockroachdb/cockroach/pkg/cmd/roachprod/main.go:1852
		  | runtime.main
		  | 	/usr/local/go/src/runtime/proc.go:204
		  | runtime.goexit
		  | 	/usr/local/go/src/runtime/asm_amd64.s:1374
		Wraps: (3) 3: dead
		Error types: (1) errors.Unclassified (2) *withstack.withStack (3) *errutil.leafError