HTTP spec (RFC 2616).

for failed imports, obscuring later attempts to import the same broken module.

'AccessControl.ZopeGuards.guarded_import' mapped some Unauthorized exceptions
onto ImportErrors:  don't do that!  Also, removed mutable defaults from
argument list, improved tests.

Protect against setNumberOfThreads disappearing after first use.

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Reinstate requestmethod doctest-as-unittest integration file, using zope.testing.doctest's backport of DocFileSuite.

- Python 2.3 doesn't support the @decorator syntax
- Owner.py methods weren't protected

Also, python 2.3's doctest module doesn't have any unittest integration,
just remove the test_requestmethod.py glue.

- Protect various security-setting-mutators with this decorator.

revert ZCatalog.getobject() semantics not to mask traversal errors and not to fallback to .resolve_url() when the traversal result is None

publish_module. Thanks to Andreas Zeidler.