How to process ThunderBird data

Hello, I met some problems when using your dataloader on Thunderbird data (data/raw/Thunderbird10M.log), with the error UnicodeDecodeError: 'utf-8' codec can't decode byte 0xa8 in position 5029: invalid start byte when f.readlines(). I have tried to modify mode 'r' to 'rb'. It didn't work. Could you please the proper dataloader to process Thunderbird data? Thanks a lot!