Type error: Cannot convert 'bytes' object to str implicitly

[Henri Devigne]

Traceback (most recent call last):
File "/usr/local/bin/tar-progress", line 11, in
sys.exit(main())
File "/usr/local/lib/python3.5/dist-packages/tar_progress/main.py", line 48, in main
archiver.create(arguments.file, arguments.compressor, arguments.files)
File "/usr/local/lib/python3.5/dist-packages/tar_progress/classes/linux.py", line 15, in create
command = "tar -cf - " + files + " | pv -s " + size + " | bzip2 > " + filename
TypeError: Can't convert 'bytes' object to str implicitly

This error append on python 3.5 and maybe in 3.6. But not on 2.7 version of python.