Ubuntu 17.04 Install dev-setup.sh ImportError: No module named _ctypes

after a git clone https://github.com/MycroftAI/mycroft-core.git and
build_host_setup_debian.sh
which went fine, I tried to run the script
dev_setup.sh

and it stopped with following output

Traceback (most recent call last): File "/home/ernst/.virtualenvs/mycroft/bin/easy_install", line 7, in <module> from setuptools.command.easy_install import main File "/home/ernst/.virtualenvs/mycroft/local/lib/python2.7/site-packages/setuptools/__init__.py", line 14, in <module> from setuptools.extension import Extension File "/home/ernst/.virtualenvs/mycroft/local/lib/python2.7/site-packages/setuptools/extension.py", line 10, in <module> from .dist import _get_unpatched File "/home/ernst/.virtualenvs/mycroft/local/lib/python2.7/site-packages/setuptools/dist.py", line 21, in <module> from setuptools import windows_support File "/home/ernst/.virtualenvs/mycroft/local/lib/python2.7/site-packages/setuptools/windows_support.py", line 2, in <module> import ctypes File "/usr/lib/python2.7/ctypes/__init__.py", line 7, in <module> from _ctypes import Union, Structure, Array ImportError: No module named _ctypes

Any hints ? TIA