These changes address inaccuracies in current messages and makes them more informative. Props birgire, garrett-eclipse, desrosj. See #43438. Built from https://develop.svn.wordpress.org/trunk@44908 git-svn-id: http://core.svn.wordpress.org/trunk@44739 1a063a9b-81f0-0310-95a4-ce76da25c4cd