Some troubles having encoding == None in
io_scene_valvesource/utils.py::90

fixed it

from
builtins.print(" ".join([str(a) for a in args]).encode(sys.getdefaultencoding()).decode(sys.stdout.encoding), end= "\n" if newline else "", flush=True)

to
builtins.print(
" ".join([str(a) for a in args]).encode(
sys.getdefaultencoding()).decode(
sys.stdout.encoding if sys.stdout.encoding != None else "UTF-8"),
end= "\n" if newline else "", flush=True)

Using last updated version, windows 10 blender 2.78