script/lint: Ensure there are files to test with pylint (#14363)

script/lint

@@ -8,7 +8,7 @@ echo '================================================='
 echo '=                FILES CHANGED                  ='
 echo '================================================='
 if [ -z "$files" ] ; then
-  echo "No python file changed. Rather use: tox -e lint"
+  echo "No python file changed. Rather use: tox -e lint\n"
   exit
 fi
 printf "%s\n" $files
@@ -19,5 +19,10 @@ flake8 --doctests $files
 echo "================"
 echo "LINT with pylint"
 echo "================"
-pylint $(echo "$files" | grep -v '^tests.*')
+pylint_files=$(echo "$files" | grep -v '^tests.*')
+if [ -z "$pylint_files" ] ; then
+  echo "Only test files changed. Skipping\n"
+  exit
+fi
+pylint $pylint_files
 echo