- The copy module now "copies" function objects (as atomic objects).
  - dict.__getitem__ now looks for a __missing__ hook before raising
    KeyError.
  - Added a new type, defaultdict, to the collections module.
    This uses the new __missing__ hook behavior added to dict (see above).

From SF patch #852334.

SF patch 825639
http://mail.python.org/pipermail/python-dev/2003-October/039445.html

Copying a new-style class that had a reference to itself didn't work.
(The same thing worked fine for old-style classes.)

and test_support.run_classtests() into run_unittest()
and use it wherever possible.

Also don't use "from test.test_support import ...", but
"from test import test_support" in a few spots.

From SF patch #662807.

atomically, but deepcopy() didn't support this at all.
I don't see any reason for this, so I'm adding ClassType
to the set of types that are deep-copied atomically.

Rewrote copy() and deepcopy() without avoidable try/except statements;
getattr(x, name, None) or dict.get() are much faster than try/except.

- subclasses of list or dict
- __reduce__ returning a 4-tuple or 5-tuple
- slots

coverage.