python2.7/subprocess.py error #29

while I use ./demo.py, and show this error:

Importing a file into MALLET: [data/demo/lda_x40_v2/corpus/corpus.txt] --> [data/demo/lda_x40_v2/model-mallet/corpus.mallet]
Traceback (most recent call last):
File "bin/train_mallet.py", line 42, in
main()
File "bin/train_mallet.py", line 39, in main
TrainMallet( args.corpus_path, args.model_path, args.token_regex, args.topics, args.iters, args.quiet, args.overwrite )
File "bin/train_mallet.py", line 25, in TrainMallet
BuildLDA( corpus_filename, model_path, tokenRegex = token_regex, numTopics = num_topics, numIters = num_iters )
File "/Users/ying-hsuanlin/termite_data_server/bin/modellers/MalletLDA.py", line 31, in init
importer.ImportFileOrFolder( tokenRegex )
File "/Users/ying-hsuanlin/termite_data_server/bin/modellers/MalletLDA.py", line 76, in ImportFileOrFolder
self.Shell( command )
File "/Users/ying-hsuanlin/termite_data_server/bin/modellers/MalletLDA.py", line 44, in Shell
p = subprocess.Popen( command, stdout = subprocess.PIPE, stderr = subprocess.STDOUT )
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 710, in init

how can i fix it? thx