-------------------
**Bug fixes**
- Fix cache heartbeat test (fixes 2107)
- Fix support of ``sqlalchemy.pool.NullPool`` for PostgreSQL backends.
The default ``pool_size`` of 25 is maintained on the default pool class
(``QueuePoolWithMaxBacklog``). When using custom connection pools, please
refer to SQLAlchemy documentation for default values.
**Internal changes**
- Remove dependency to kinto-redis in core tests