on various platforms, most recently the Alpha Tru64.

test_itimer_prof.

Rebuild the DocTestSuite on each iteration.

When cls is an ABCMeta, every call to isinstance(x, cls)
records type(x) in the cls._abc_cache of cls_abc_negative_cache.
So we clear these caches at the end of the test.

inspect.isabstract() is not the correct test for all ABCs, because there is no @abstractmethod in io.py (why?)
isinstance(cls, ABCMeta) would be more exact, but it fails with an infinite recursion.
So I used a hack to determine whether a class is an ABCMeta.

The true correction would be to turn cls._abc_cache &co into a WeakSet, as py3k does.
But classic classes are not weak referenceable...

Of course, this change should not be merged into the py3k branch.

it registers the same codec on each iteration.
Do it only once at load time.

with python 2.6, enumerating bytes yields 1-char strings, not numbers.

Don't merge this into the py3k branch.

of effort to do so.