The test failed on branch=master, cloud=gce:
test artifacts and logs in: artifacts/acceptance/version-upgrade/run_1
	versionupgrade.go:280,versionupgrade.go:428,versionupgrade.go:410,versionupgrade.go:186,versionupgrade.go:174,acceptance.go:58,acceptance.go:95,test_runner.go:754: dial tcp 127.0.0.1:26261: connect: connection refused

	cluster.go:1612,context.go:135,cluster.go:1601,test_runner.go:823: dead node detection: /go/src/github.com/cockroachdb/cockroach/bin/roachprod monitor local --oneshot --ignore-empty-nodes: exit status 1 2: 22731
		4: 22542
		3: dead
		1: 22829
		Error: UNCLASSIFIED_PROBLEM: 3: dead
		(1) UNCLASSIFIED_PROBLEM
		Wraps: (2) attached stack trace
		  | main.glob..func14
		  | 	/go/src/github.com/cockroachdb/cockroach/pkg/cmd/roachprod/main.go:1143
		  | main.wrap.func1
		  | 	/go/src/github.com/cockroachdb/cockroach/pkg/cmd/roachprod/main.go:267
		  | github.com/spf13/cobra.(*Command).execute
		  | 	/go/pkg/mod/github.com/spf13/cobra@v0.0.5/command.go:830
		  | github.com/spf13/cobra.(*Command).ExecuteC
		  | 	/go/pkg/mod/github.com/spf13/cobra@v0.0.5/command.go:914
		  | github.com/spf13/cobra.(*Command).Execute
		  | 	/go/pkg/mod/github.com/spf13/cobra@v0.0.5/command.go:864
		  | main.main
		  | 	/go/src/github.com/cockroachdb/cockroach/pkg/cmd/roachprod/main.go:1839
		  | runtime.main
		  | 	/usr/local/go/src/runtime/proc.go:203
		  | runtime.goexit
		  | 	/usr/local/go/src/runtime/asm_amd64.s:1357
		Wraps: (3) 3 safe details enclosed
		Wraps: (4) 3: dead
		Error types: (1) errors.Unclassified (2) *withstack.withStack (3) *safedetails.withSafeDetails (4) *errors.errorString