func TestClientUnsupportedKex(t *testing.T) {
	if os.Getenv("GO_BUILDER_NAME") != "" {
		t.Skip("skipping known-flaky test on the Go build dashboard; see golang.org/issue/15198")
	}
	config := &ClientConfig{
		User: "testuser",
		Auth: []AuthMethod{
			PublicKeys(),
		},
		Config: Config{
			KeyExchanges: []string{"diffie-hellman-group-exchange-sha256"}, // not currently supported
		},
		HostKeyCallback: InsecureIgnoreHostKey(),
	}
	if err := tryAuth(t, config); err == nil || !strings.Contains(err.Error(), "common algorithm") {
		t.Errorf("got %v, expected 'common algorithm'", err)
	}
}