Rename TestCase._result to _resultForDoCleanups to avoid potential clashes in TestCase subclasses. Issue 6072.

a code object.

to make it possible to use pydoc to get access to the language reference.

That is, without this patch the folllowing won't work:

   >>> help('if')

made it try to set the line number from the trace callback for a 'call' event.
This patch makes the error message a little more helpful in that case, and
makes it a little less likely that a future editor will make the same mistake
in test_trace.

removed sys.platform == 'mac' support in distutils.dist.parse_command_line and improved test coverage

complex -> float conversion error messages.