Add back License not handled by a script

See #3516 (comment)

Author: Pierre-Sassoulas

pylint/lint/check_parallel.py

@@ -1,3 +1,6 @@
+# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+# For details: https://github.com/PyCQA/pylint/blob/master/COPYING
+
 import collections
 import functools
 

pylint/lint/report_functions.py

@@ -1,3 +1,6 @@
+# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+# For details: https://github.com/PyCQA/pylint/blob/master/COPYING
+
 import collections
 
 from pylint import checkers, exceptions

pylint/lint/run.py

@@ -1,3 +1,6 @@
+# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+# For details: https://github.com/PyCQA/pylint/blob/master/COPYING
+
 import os
 import sys
 

pylint/lint/utils.py

@@ -1,3 +1,6 @@
+# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+# For details: https://github.com/PyCQA/pylint/blob/master/COPYING
+
 import contextlib
 import sys