Python error

[scriptzteam]

/btctxstore/examples# python storenulldata.py
Traceback (most recent call last):
File "storenulldata.py", line 9, in
from btctxstore import BtcTxStore
File "/usr/local/lib/python2.7/dist-packages/btctxstore-4.8.0-py2.7.egg/btctxstore/init.py", line 6, in
from btctxstore.api import BtcTxStore
File "/usr/local/lib/python2.7/dist-packages/btctxstore-4.8.0-py2.7.egg/btctxstore/api.py", line 12, in
from btctxstore import deserialize
File "/usr/local/lib/python2.7/dist-packages/btctxstore-4.8.0-py2.7.egg/btctxstore/deserialize.py", line 22, in
from . import common
File "/usr/local/lib/python2.7/dist-packages/btctxstore-4.8.0-py2.7.egg/btctxstore/common.py", line 11, in
from pycoin.encoding import byte_to_int
ImportError: cannot import name byte_to_int