Fix tests which call str() on exception messages

Since Pytest 5, `ExceptionInfo` objects (returned by `pytest.raises`) now
have the same `str` representation as `repr`. This means that `str(e)`
now needs to be changed to `str(e.value)`.

https://github.com/pytest-dev/pytest/issues/5412

tests/app/dao/test_services_dao.py

@@ -503,7 +503,7 @@ def test_dao_fetch_live_services_data(sample_user):
 def test_get_service_by_id_returns_none_if_no_service(notify_db):
     with pytest.raises(NoResultFound) as e:
         dao_fetch_service_by_id(str(uuid.uuid4()))
-    assert 'No row was found for one()' in str(e)
+    assert 'No row was found for one()' in str(e.value)
 
 
 def test_get_service_by_id_returns_service(notify_db_session):