knee.py, a Python re-implementation of hierarchical module import was
removed from the standard library because it no longer functioned properly.
deepreload.py is little more than a hacked version of knee.py which overrides
__builtin__.__import__ to ensure that each module is re-imported once (before
just referring to sys.modules as usual).
In addition, `os.path` was added to the default excluded modules, since
somehow it has an entry in sys.modules without `os' being a package.