README: ansible 2.7 is not supported

README.md

@@ -61,7 +61,7 @@ Install base dependencies:
 
 Requirements:
 
-- Ansible >= 2.6.2
+- Ansible >= 2.6.2, Ansible 2.7 is not yet supported and known to fail
 - Jinja >= 2.7
 - pyOpenSSL
 - python-lxml