Log Message:
py-peewee: updated to 3.15.3

3.15.3

* Add `scalars()` query method (complements `scalar()`), roughly equivalent to
  writing `[t[0] for t in query.tuples()]`.
* Small doc improvements
* Fix and remove some flaky test assertions with Sqlite INSERT + RETURNING.
* Fix innocuous failing Sqlite test on big-endian machines.