Log Message:
py-peewee: updated to 3.9.3

3.9.3
* Added cross-database support for NULLS FIRST/LAST when specifying the
  ordering for a query. Previously this was only supported for Postgres. Peewee
  will now generate an equivalent CASE statement for Sqlite and MySQL.
* Added [EXCLUDED](http://docs.peewee-orm.com/en/latest/peewee/api.html#EXCLUDED)
  helper for referring to the EXCLUDED namespace used with INSERT...ON CONFLICT
  queries, when referencing values in the conflicting row data.
* Added helper method to the model Metadata class for setting the table name
  at run-time. Setting the Model._meta.table_name directly may have appeared
  to work in some situations, but could lead to subtle bugs. The new API is
  Model._meta.set_table_name().
* Enhanced helpers for working with Peewee interactively, [see \ 
doc](http://docs.peewee-orm.com/en/latest/peewee/interactive.html).
* Fix cache invalidation bug in DataSet that was originally reported on the
  sqlite-web project.
* New example script implementing a [hexastore]