Fix unlink date range type.

date_range/models/date_range.py

@@ -18,7 +18,8 @@ class DateRange(models.Model):
     date_start = fields.Date(string='Start date', required=True)
     date_end = fields.Date(string='End date', required=True)
     type_id = fields.Many2one(
-        comodel_name='date.range.type', string='Type', index=1, required=True)
+        comodel_name='date.range.type', string='Type', index=1, required=True,
+        ondelete='restrict')
     type_name = fields.Char(
         string='Type', related='type_id.name', readonly=True, store=True)
     company_id = fields.Many2one(

date_range/tests/test_date_range_type.py

@@ -2,6 +2,8 @@
 # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl)
 
 from odoo.tests.common import TransactionCase
+from odoo.tools import mute_logger
+from psycopg2 import IntegrityError
 
 
 class DateRangeTypeTest(TransactionCase):
@@ -17,3 +19,17 @@ class DateRangeTypeTest(TransactionCase):
              'company_id': False,
              'allow_overlap': False})
         self.assertFalse(drt.company_id)
+
+    def test_unlink(self):
+        date_range = self.env['date.range']
+        drt = self.env['date.range.type'].create(
+            {'name': 'Fiscal year',
+             'allow_overlap': False})
+        date_range.create({
+            'name': 'FS2016',
+            'date_start': '2015-01-01',
+            'date_end': '2016-12-31',
+            'type_id': drt.id,
+        })
+        with self.assertRaises(IntegrityError), mute_logger('odoo.sql_db'):
+            drt.unlink()