TypeError: exceptions must be strings, classes, or instances, not type

Hi, I'm trying to use this Pyrex module:

http://code.google.com/p/pypcap/

but I get:

Traceback (most recent call last):
   File "./analyze.py", line 11, in <module>
     for x in pc: xs.append(x)
   File "pcap.pyx", line 346, in pcap.pcap.__next__
TypeError: exceptions must be strings, classes, or instances, not type

because the places marked "here" below are apparently doing something 
that Pyrex can't handle:

     def __next__(self):
         cdef pcap_pkthdr *hdr
         cdef char *pkt
         cdef int n
         while 1:
             Py_BEGIN_ALLOW_THREADS
             n = pcap_ex_next(self.__pcap, &hdr, &pkt)
             Py_END_ALLOW_THREADS
             if n == 1:
                 return (hdr.ts.tv_sec + (hdr.ts.tv_usec / 1000000.0),
                         PyBuffer_FromMemory(pkt, hdr.caplen))
             elif n == -1:
                 raise KeyboardInterrupt # here
             elif n == -2:
                 raise StopIteration # here

Does anybody know what's going on? Are exceptions not allowed in Pyrex? 
Is there a workaround?

Thanks in advance for any answers!
-- 
Yang Zhang
http://www.mit.edu/~y_z/