umm

import builtin as __builtins__;
cdef const str __name__ = "nullstr";
cdef const str __nullstrtyperrmsg__ = "nullstrtype obj cannot be an str";
cdef const TypeError __nullstrtyperr__ = TypeError(__nullstrtyperrmsg__);

cdef class nullstrtype(str):
    cdef None __str__(nullstrtype self):
        raise __nullstrtyperr__;
    cdef str __repr__(nullstrtype self):
        return __name__;

cdef const nullstrtype __builtins__.nullstr = nullstrtype();