Return self when fullname starts with root_name and the
        target module is one vendored through this importer.

def find_module(self, fullname, path=None):
        """
        Return self when fullname starts with root_name and the
        target module is one vendored through this importer.
        """
        root, base, target = fullname.partition(self.root_name + '.')
        if root:
            return
        if not any(map(target.startswith, self.vendored_names)):
            return
        return self