'See L{IReactorPluggableResolver}.
@param resolver: see L{IReactorPluggableResolver}.
@return: see L{IReactorPluggableResolver}.'

def installResolver(self, resolver):

    assert IResolverSimple.providedBy(resolver)
    oldResolver = self.resolver
    self.resolver = resolver
    self._nameResolver = _SimpleResolverComplexifier(resolver)
    return oldResolver
