Repair lint_po when used in a pre-commit hook

Fixes a regression introduced by the fix for #17359: when using the recommended pre-commit hook, that fix prevents creating commits that do not modify any PO file.

Repair lint_po when used in a pre-commit hook
Fixes a regression introduced by the fix for #17359: when using the recommended pre-commit hook, that fix prevents creating commits that do not modify any PO file.
c4d6588f · intrigeri · 5befa2d6 · af71169b
Commit c4d6588f authored Jan 02, 2020 by intrigeri
--- a/jenkins-tools @ af71169b
+++ b/jenkins-tools @ af71169b
-Subproject commit a342116e1de74d3f331a87eb01e51db99682d670
+Subproject commit af71169b692fa19bc66b3f67350e8be58efbb30d