Hello,
I'm having the same problem as in [#12019](https://github.com/ansible/ansible/issues/12019) but with a newer version of ansible. I'm writing here as [@jimi-c](https://github.com/jimi-c) warns about people not reading comments to closed issues.
I have ansible 1.9.3 and redis but it doesn't work.
$ ansible --version
ansible 1.9.3
configured module search path = None
$ python -c "import redis ; print 'ok'"
ok
$ ansible-playbook testset.yml --dry-run
The 'redis' python module is required, 'pip install redis'
Do you have any idea of how to proceed