chore(test): fix a DeprecationWarning

--HG--
branch : 0.1

test/test_mappers.py

@@ -264,7 +264,7 @@ class CompoundMapperTC(CubicWebTC):
             relations = ('flash', )
 
         expected_regexp = 'duplicate relation mapping for "Photo": flash'
-        with self.assertRaisesRegexp(ValueError, expected_regexp):
+        with self.assertRaisesRegex(ValueError, expected_regexp):
             bad_compound.__registered__(self.vreg['mappers'])
 
     def test_mapped_attributes_hidden(self):