Relicense to LGPL

With the agreement of authors and contributors.
Closes #635 (https://github.com/OCA/server-tools/issues/635)

base_external_dbsource/models/base_external_dbsource.py

@@ -1,27 +1,11 @@
 # -*- coding: utf-8 -*-
-##############################################################################
-#
-#    Daniel Reis
-#    2011
-#
-#    This program is free software: you can redistribute it and/or modify
-#    it under the terms of the GNU Affero General Public License as
-#    published by the Free Software Foundation, either version 3 of the
-#    License, or (at your option) any later version.
-#
-#    This program is distributed in the hope that it will be useful,
-#    but WITHOUT ANY WARRANTY; without even the implied warranty of
-#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-#    GNU Affero General Public License for more details.
-#
-#    You should have received a copy of the GNU Affero General Public License
-#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-##############################################################################
+# Copyright 2011 Daniel Reis
+# License LGPL-3.0 or later (http://www.gnu.org/licenses/lgpl).
 
 import os
 import logging
 import psycopg2
+
 from odoo import models, fields, api,  _
 from odoo.exceptions import Warning as UserError
 import odoo.tools as tools