Fix confusing test failure message

Resolves #10466.

Signed-off-by: Simon Alling <alling.simon@gmail.com>

cmd/helm/helm_test.go

@@ -60,8 +60,11 @@ func runTestCmd(t *testing.T, tests []cmdTestCase) {
 				}
 				t.Logf("running cmd (attempt %d): %s", i+1, tt.cmd)
 				_, out, err := executeActionCommandC(storage, tt.cmd)
-				if (err != nil) != tt.wantError {
-					t.Errorf("expected error, got '%v'", err)
+				if tt.wantError && err == nil {
+					t.Errorf("expected error, got success with the following output:\n%s", out)
+				}
+				if !tt.wantError && err != nil {
+					t.Errorf("expected no error, got: '%v'", err)
 				}
 				if tt.golden != "" {
 					test.AssertGoldenString(t, out, tt.golden)