from https://bitbucket.org/zzzeek/sqlalchemy/issues/3297

primary key that has values for some but not all of the PK fields
would emit a SELECT statement leaking the internal NEVER_SET symbol
into the query, rather than detecting that this object does not have
a searchable primary key and no SELECT should be emitted.
fixes #3647

INSERT, UPDATE, and DELETE statements to both specify their own
WITH clause, as well as for these statements themselves to be
CTE expressions when they include a RETURNING clause.
fixes #2551

that this structure is only intended to track additions
and removals from the dictionary, not recursive tracking
of embedded changes.  fixes #3646.

because we never log in on the ts1/ts2.  races against other runs
and erases their DBs

expression would not escape properly, e.g. ``some\:\:expr``, as is most
commonly required when rendering Postgresql-style CAST expressions.
fixes #3644

:meth:`.Query.distinct` is combined with :meth:`.Query.order_by` such
that columns which are already present will not be added
a second time, even if they are labeled with a different name.
Regardless of this change, the extra columns added to the SQL have
never been returned in the final result, so this change only impacts
the string form of the statement as well as its behavior when used in
a Core execution context.   Additionally, columns are no longer added
when the DISTINCT ON format is used, provided the query is not
wrapped inside a subquery due to joined eager loading.
fixes #3641

yet cx_Oracle still has open sessions that cannot be killed until process dies.
Oracle wins!   Add a completely separate DB reaper script that runs
after py.test is done.