Bug 1622328 - export_telemetry_schema.py: Add the license r=Callek

Depends on D66806

Differential Revision: https://phabricator.services.mozilla.com/D66807

python/mozbuild/mozbuild/export_telemetry_schema.py

@@ -1,4 +1,8 @@
 #!/usr/bin/env python
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
 
 from __future__ import absolute_import, print_function, unicode_literals