Output a message when a hook fails due to file modification

testing/resources/modified_file_returns_zero_repo/bin/hook3.sh

@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+
+for f in $@; do
+    # Non UTF-8 bytes
+    echo -e '\x01\x97' > "$f"
+done

testing/resources/modified_file_returns_zero_repo/hooks.yaml

@@ -2,9 +2,14 @@
     name: Bash hook
     entry: bin/hook.sh
     language: script
-    files: ''
+    files: 'foo.py'
 -   id: bash_hook2
     name: Bash hook
     entry: bin/hook2.sh
     language: script
     files: ''
+-   id: bash_hook3
+    name: Bash hook
+    entry: bin/hook3.sh
+    language: script
+    files: 'bar.py'