fix(parsers.nagios): nagios parser now uses real error for logging in…

…fluxdata#10472 (influxdata#10473)

plugins/parsers/nagios/parser.go

@@ -28,7 +28,7 @@ func getExitCode(err error) (int, error) {
 		// If it is not an *exec.ExitError, then it must be
 		// an io error, but docs do not say anything about the
 		// exit code in this case.
-		return 0, errors.New("expected *exec.ExitError")
+		return 0, err
 	}
 
 	ws, ok := ee.Sys().(syscall.WaitStatus)

plugins/parsers/nagios/parser_test.go

@@ -33,7 +33,7 @@ func TestGetExitCode(t *testing.T) {
 				return errors.New("I am not *exec.ExitError")
 			},
 			expCode: 0,
-			expErr:  errors.New("expected *exec.ExitError"),
+			expErr:  errors.New("I am not *exec.ExitError"),
 		},
 	}
 
@@ -177,7 +177,7 @@ func TestTryAddState(t *testing.T) {
 						n("nagios").
 						f("perfdata", 0).b(),
 				}
-				expErr := "exec: get exit code: expected *exec.ExitError"
+				expErr := "exec: get exit code: non parsable error"
 
 				assertEqual(t, exp, metrics)
 				require.Equal(t, expErr, err.Error())