The check for whether a README.rst exists would naively look for
files like __init__.py/README.rst if there were files in the roles/
directory. Only look for role directories instead.
This modifies autoroles to raise a warning when it finds a role
without a README.rst file. This can be disabled with a config option
if you wish to build with warning-as-error but don't wish to document
Fix a typo in the readme for the zuul_role_paths
Add a test for the autoroles path detection by including a roles
directory under a subdir. Manually removing the README.rst file has
validated that the warning is triggered.