* Make LookupBase an abc with required methods (run()) marked as an
  abstractmethod
* Mark methods that don't use self as @staticmethod
* Document how to implement the run method of a lookup plugin.

Add mention of roles_path parameter to `ansible-galaxy install` command

Fixes #12464

Fix for user defined modules not overriding modules from core.

This fix takes into account that powershell modules are somewhat
different than regular modules and have to be kept separate.

Fixes #12465

Python 3: there's no basestring

Fix option descriptions in ansible-doc output

Fixes #12462.

Fixes #12460

Fixes one failing test.

Now technically a filename can be a bytestring, even on Python 3.  I
hope this is unlikely for Ansible.

Without rebreaking #12055

Fixes #ansible-modules-core/2098

Detect if core modules aren't installed and warn if that is the  case

Fixes #11206

Fix typo

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