usfm2osis processes usfm files forever

I have created a test case where the script usfm2osis.py keeps processing the input usfm files forever. Each time I interrupt the script through Ctrl-C, it stops at the same line numbers:

Sorting book files canonically
Converting USFM documents to OSIS...
^CProcess Worker-1:
Traceback (most recent call last):
Traceback (most recent call last):
File "usfm2osis.py", line 1568, in <module>
File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
self.run()
File "usfm2osis.py", line 1450, in run
k,v=result_queue.get()
File "/usr/lib/python2.7/multiprocessing/queues.py", line 117, in get
res = self._recv()
KeyboardInterrupt
osis = convertToOsis(job)
File "usfm2osis.py", line 1343, in convertToOsis
osis = cvtPrivateUseExtensions(osis, relaxedConformance)
File "usfm2osis.py", line 1198, in cvtPrivateUseExtensions
osis = re.sub(r'\z([^\s])\s(.?)(\z\1*)', r'<seg type="x-\1">\2</seg>', osis, flags=re.DOTALL)
File "/usr/lib/python2.7/re.py", line 151, in sub
return _compile(pattern, flags).sub(repl, string, count)
KeyboardInterrupt

This happens on Ubuntu 12.10 64 bits and Python 2.7.3.

The test case can be downloaded from the following URL:

http://bibleconsultants.dyndns.org/downloads/temporal/usfm2osis4ever.zip

Steps:
1. Download and unzip usfm2osis4ever.zip
2. Go into folder usfm2osis
3. Run ./test
Result:
It keeps processing forever.
Expected result:
It converts the USFM files to OSIS and completes normally.