Comment 4 for bug 1776634

This is a problem with pip 10:
https://github.com/pypa/pip/issues/4805

Suggestions are to delete it manually:
http://eavesdrop.openstack.org/irclogs/%23openstack-dib/%23openstack-dib.2018-06-12.log.html#t2018-06-12T07:32:20

Others suggested to downgrade:
https://github.com/pypa/pip/issues/5247
https://stackoverflow.com/questions/49911550/how-to-upgrade-disutils-package-pyyaml

Downgrading to 9.0.1 before executing this step:
https://github.com/openstack/heat-agents/blob/master/heat-config/install.d/heat-config-source-install/50-heat-config-soure
fixed it for me.