How to test an ansible playbook using molecule inside docker locally?

When molecule is run on travis, the build is successful:

```
$ molecule test
--> Validating schema /home/travis/build/030/ansible-firefox/molecule/default/molecule.yml.
Validation completed successfully.
--> Test matrix

└── default
├── lint
├── destroy
├── dependency
├── syntax
├── create
├── prepare
├── converge
├── idempotence
├── side_effect
├── verify
└── destroy

--> Scenario: 'default'
--> Action: 'lint'
--> Executing Yamllint on files found in /home/travis/build/030/ansible-firefox/...
Lint completed successfully.
--> Executing Flake8 on files found in /home/travis/build/030/ansible-firefox/molecule/default/tests/...
Lint completed successfully.
--> Executing Ansible Lint on /home/travis/build/030/ansible-firefox/molecule/default/playbook.yml...

Lint completed successfully.
--> Scenario: 'default'
--> Action: 'destroy'

PLAY [Destroy] *

TASK [Destroy molecule instance(s)] ****
changed: [localhost] => (item=None)
changed: [localhost]

TASK [Wait for instance(s) deletion to complete] *
ok: [localhost] => (item=None)
ok: [localhost]

TASK [Delete docker network(s)] ****

PLAY RECAP *****
localhost : ok=2 changed=1 unreachable=0 failed=0

--> Scenario: 'default'
--> Action: 'dependency'
Skipping, missing the requirements file.
--> Scenario: 'default'
--> Action: 'syntax'

playbook: /home/travis/build/030/ansible-firefox/molecule/default/playbook.yml

--> Scenario: 'default'
--> Action: 'create'

PLAY [Create]

TASK [Log into a Docker registry]
skipping: [localhost] => (item=None)

Your molecule run is failing in a very early stage, when it first tries to delete a possibly existing container before starting everything over.

Since you have a default configuration and your make a normal run of molecule, there is absolutely no valuable output in your log.

You have to run molecule in --debug mode to get something usable. And I'd bet a case of champagne that the error you will see poping out is that ansible is not able to find docker or docker-py.

If I'm right, your solution will then be pip install docker

StackExchange DevOps Q#5403, answer score: 1