Follow up to 8769f03c, which allows the undefined var error to be raised
if we're getting vars with a full context (play/host/task) and the host
has already gathered facts. In this way, vars_files containing variables
that fail to be templated are not silently ignored.

Python 3: there is no 'basestring'

Fixes #12449

Close module file once we're done reading from it

This fixes a failing unit test.

In actual use (which is still quite far), I'm not sure if bytes ->
unicode conversion should be done here (in which case the code will fail
with an AttributeError: 'bytes' object has no attribute 'readlines'), or
inside self._connection.exec_command() (in which case my change is
correct).

Use dict.get()

Stops using _groups_list to check for host when using 'add_host'

Fix typo, remove redundant paragraph

Fixes #12437

Fixes #12427

Python 3: there's no xrange

Support «hosts: foo[1:]» and add tests for split/apply_subscript

Now, instead of relying on hostvars on the executor side, we compile
the vars for the delegated to host in a special internal variable and
have the PlayContext object look for things there when applying task/
var overrides, which is much cleaner and takes advantage of the code
already dealing with all of the magic variable variations.

Fixes #12127
Fixes #12079

* Clearing interpreter settings from variables, so those set for the
  original host aren't incorrectly applied to the delegated to host
* Fixed incorrect string for remote user in delegated hosts hostvars
* Properly looking for multiple possiblities in the delegated-to hosts
  hostvars (ansible_ssh_host vs. ansible_host)

Fix example formatting in the documentation

added new module object to vca

initial add of vca common module

fixes #12434

Use six.moves.range instead (aliased to xrange on Python 2, aliased to
range on Python 3).

Also I couldn't resist replacing the elaborate chr/ord/randrange dance
with the simpler random.choice(string.ascii_lowercase) that was already
used elsewhere in the Ansible codebase.

Fixes #12349

Allow env-setup to use spaces in full path

Same fix as was applied in f162990c to the action plugin

Fixes #12355

Tested.  Thanks for spotting and then fixing this -- Allow hexadecimal ranges in IPv6 addresses, not only 0-9

Remove deprecation warning; now handled in _split_patterns