Print stacktrace to stderr for easier readability (#5616)

Signed-off-by: Danny Kopping <danny.kopping@grafana.com>

pkg/util/log/log.go

@@ -97,7 +97,10 @@ func CheckFatal(location string, err error, logger log.Logger) {
 		logger = log.With(logger, "msg", "error "+location)
 	}
 	// %+v gets the stack trace from errors using github.com/pkg/errors
-	logger.Log("err", fmt.Sprintf("%+v", err))
+	errStr := fmt.Sprintf("%+v", err)
+	fmt.Fprintln(os.Stderr, errStr)
+
+	logger.Log("err", errStr)
 	os.Exit(1)
 }