support within Python 2.x; move away from character semantics which Oracle is
deprecating anyway to byte semantics which should hopefully eliminate the
problem with a backend character set of UTF-8.
the rollback; unfortunately, Oracle decides to commit data even when dropping
a connection from the pool instead of rolling it back so the attempt still
has to be made.
VanderWoude; this value is retained as a convenience to the user and not used
by anything in the module; if changed externally it may be convenient to keep
this copy up to date.
