Fail if dirty (#16839)

* Fail if dirty

* Update check_dirty

* Update text

* Fix comment

* Add -e

* Update dirty script

script/check_dirty

@@ -0,0 +1,7 @@
+#!/bin/bash
+[[ -z $(git ls-files --others --exclude-standard) ]] && exit 0
+
+echo -e '\n***** ERROR\nTests are leaving files behind. Please update the tests to avoid writing any files:'
+git ls-files --others --exclude-standard
+echo
+exit 1