Log total error count in eslint failure message

build/eslint.js

@@ -14,7 +14,7 @@ function eslint() {
 		.pipe(
 			eslint((results) => {
 				if (results.warningCount > 0 || results.errorCount > 0) {
-					throw new Error('eslint failed with warnings and/or errors');
+					throw new Error(`eslint failed with ${results.warningCount + results.errorCount} warnings and/or errors`);
 				}
 			})
 		).pipe(es.through(function () { /* noop, important for the stream to end */ }));