Cannot pull ansible docker image
If run you docker pull &lt;image&gt;, you are implicitly asking for a tag named latest.  There is no such tag available from the Ansible repository.  You can see a list of available tags at https://hub.docker.com/r/ansible/ansible/tags/.

For example, if you wanted the fedora27py3 version of the image, you would run:

docker pull ansible/ansible:fedora27py3


I note that the most recent of thoses images is 7 months old. If you're experimenting iwth Ansible you might want to just install it into a Python virtual environment.