Fixes the bug I introduced in my previous commit (six.string_types is
(basestring,) on Python 2).  Thanks @abadger for noticing!

Replace 'unicode' with six.text_type, everywhere but in module_utils.

Replace .iteritems() with six.iteritems() everywhere except in
module_utils (because there's no 'six' on the remote host).  And except
in lib/ansible/galaxy/data/metadata_template.j2, because I'm not sure
six is available there.

This fixes the remaining Python 3 syntax errors, so re-enable compileall
for contrib/ again.

types.NoneType was removed in Python 3.

None is a singleton in Python, so 'x is None' is equivalent to
'isinstance(x, NoneType)'.

A future branch might make it configurable.

Also, use old school string interpolation so that the plugin is compatible with
Python < 2.7.

Updates to Windows Azure inventory script from Tower. Includes changes from https://github.com/ansible/ansible/pull/8403.

Openstack inventory updates from Tower.  Includes changes from https://github.com/ansible/ansible/pull/10491 and https://github.com/ansible/ansible/pull/10776.

Added _meta dictionary with hostvars in --list json output.

Paramiko module is used to parse ssh_config.
Added multi-vm support
Added "_meta" element https://docs.ansible.com/ansible/developing_inventory.html#tuning-the-external-inventory-script

https://github.com/ansible/ansible/issues/10840
before
RDS: `ERROR: Inventory script (ec2.py) had an execution error: Forbidden`
EC2: `ERROR: Inventory script (ec2.py) had an execution error: Error connecting to AWS backend.
You are not authorized to perform this operation.`
after
RDS: `ERROR: Inventory script (ec2.py) had an execution error: ERROR: "Forbidden", while: getting RDS instances`
EC2: `ERROR: Inventory script (ec2.py) had an execution error: ERROR: "Error connecting to AWS backend.
You are not authorized to perform this operation.", while: getting EC2 instances`