Bump PyYaml version to 6.0 only for py3.6+ (#1376)
Bump PyYaml version to 6.0 only for py3.6+ (#1376)

* Bump PyYaml version to 6.0 only for py3.6+
* Pin jinja2 to 2.11.3
cloudify-cosmo/cloudify-cli,cloudify-cosmo/cloudify-cli