import sys, imp

__path__ = [ '/tmp/test' ]

class TestLoader(object):
    def __init__(self, file, filename, stuff):
        self.file = file
        self.filename = filename
        self.stuff = stuff

    def load_module(self, fullname):
        mod = imp.load_module(fullname, self.file, self.filename, self.stuff)
        if self.file:
            self.file.close()
        mod.__loader__ = self  # for introspection
        return mod

class TestImporter(object):
    def __init__(self, path):
        print('TestImporter %r\n' % path)
        if path not in ['/tmp/test']:
            raise ImportError

    def find_module(self, fullname, path=None):
        print('find_module %r %r %r\n' % ( fullname, path, __path__))
        if not fullname.startswith('testimport'):
            return None

        _, mod_name = fullname.rsplit('.',1)
        found = imp.find_module(mod_name, path or ['/tmp/test'])
        print('%r\n' % (found,))

        return TestLoader(*found)

sys.path_hooks.insert(0,TestImporter)
sys.path_importer_cache = {}

import testimport.foo