Not able to use create_corpus.py or create_hdf5.py to create a .hdf5 file

Whenever I try to use the commands in https://github.com/bhoov/exbert/blob/master/server/data_processing/README.md to create a corpus with a text file as input. (P.S. I have tried all types of text files. Big, small, english, non english.) While creating the hdf5 file, the following error always comes up: 

"TypeError: Can't implicitly convert non-string objects to strings"