Meta: Only complain about linter tools if relevant files have changed

Meta/lint-python.sh

@@ -5,11 +5,6 @@ set -e
 script_path=$(cd -P -- "$(dirname -- "$0")" && pwd -P)
 cd "${script_path}/.." || exit 1
 
-if ! command -v flake8 >/dev/null 2>&1 ; then
-    echo "flake8 is not available. Either skip this script, or install flake8."
-    exit 1
-fi
-
 if [ "$#" -eq "0" ]; then
     mapfile -t files < <(
         git ls-files '*.py'
@@ -24,6 +19,11 @@ else
 fi
 
 if (( ${#files[@]} )); then
+    if ! command -v flake8 >/dev/null 2>&1 ; then
+        echo "flake8 is not available, but python files need linting! Either skip this script, or install flake8."
+        exit 1
+    fi
+
     flake8 "${files[@]}" --max-line-length=120
 else
     echo "No py files to check."