gunicorn py3

When install gunicorn with python3, e.g. pip3 install gunicorn, and run it

it still runs under python2 context somehow, so if the web app is using py3 libraries it would fail complaining about "not found module".

One way is to use python virtualenv, and run from there

Another way is to uninstall any gunicorn version from py2 or yum

  pip uninstall gunicorn 

or 

 yum uninstall gunicorn

Then install it again with py3

  pip3 install gunicorn

Finally, need to run it with the abosolute path:

/usr/local/bin/gunicorn  -b 0.0.0.0:8080  your_app:app