Prepare the six and python 2.7 support dropping
Prepare the six and python 2.7 support dropping

With python 3 the input function is safe.
The six dropping will re-introduce the usage of the input function
and bandit checks will fails.

We drop python 2.7 support so we ignore the bandit check B322 [1] before
starting to drop six support.

[1] https://bandit.readthedocs.io/en/latest/blacklists/blacklist_calls.html#b322-input

Change-Id: Ie956a65ebc4c781c5e661e8021f674833be8b323

openstack/heat,openstack/heat