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##### SUMMARY
<!--- Explain the problem briefly below -->

I get an `ERROR! Unexpected Exception, this is probably a bug: 'Block' object has no attribute 'get_search_path'`.  It seems to require both an 'apply' on include_tasks and the `playbook_vars_root` configuration option set to trigger the exception.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->

Core

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible 2.9.2
  config file = ./ansible.cfg
  configured module search path = ['/root/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/local/virtualenv/py3/ansible_stable/lib/python3.7/site-packages/ansible
  executable location = /usr/local/virtualenv/py3/ansible_stable/bin/ansible
  python version = 3.7.3 (default, Apr  3 2019, 05:39:12) [GCC 8.3.0]

```

##### CONFIGURATION

    PLAYBOOK_VARS_ROOT(./ansible.cfg) = all

##### OS / ENVIRONMENT

Debian 10 ansible latest version of ansible installed via pip into venv.

##### STEPS TO REPRODUCE

ansible-playbook example.yml -vvv 2>&1

    ansible-playbook 2.9.2
      config file = ./ansible.cfg
      configured module search path = ['/root/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
      ansible python module location = /usr/local/virtualenv/py3/ansible_stable/lib/python3.7/site-packages/ansible
      executable location = /usr/local/virtualenv/py3/ansible_stable/bin/ansible-playbook
      python version = 3.7.3 (default, Apr  3 2019, 05:39:12) [GCC 8.3.0]
    Using ./ansible.cfg as config file
    host_list declined parsing /etc/ansible/hosts as it did not pass its verify_file() method
    script declined parsing /etc/ansible/hosts as it did not pass its verify_file() method
    auto declined parsing /etc/ansible/hosts as it did not pass its verify_file() method
    Parsed /etc/ansible/hosts inventory source with ini plugin
    [WARNING]: provided hosts list is empty, only localhost is available. Note that the implicit localhost does not match
    'all'

    PLAYBOOK: example.yml *************************************************************************************************
    1 plays in example.yml

    PLAY [localhost] ******************************************************************************************************
    META: ran handlers

    TASK [ssh_client : No exception] **************************************************************************************
    task path: ./roles/ssh_client/tasks/main.yml:2
    included: ./roles/ssh_client/tasks/clean_known_hosts.yml for localhost

    TASK [ssh_client : Read /etc/ssh/ssh_known_hosts] *********************************************************************
    task path: ./roles/ssh_client/tasks/clean_known_hosts.yml:2
    <127.0.0.1> ESTABLISH LOCAL CONNECTION FOR USER: root
    <127.0.0.1> EXEC /bin/sh -c 'echo ~root && sleep 0'
    <127.0.0.1> EXEC /bin/sh -c '( umask 77 && mkdir -p "` echo /root/.ansible/tmp/ansible-tmp-1576004604.8780084-124655683624288 `" && echo ansible-tmp-1576004604.8780084-124655683624288="` echo /root/.ansible/tmp/ansible-tmp-1576004604.8780084-124655683624288 `" ) && sleep 0'
    Using module file /usr/local/virtualenv/py3/ansible_stable/lib/python3.7/site-packages/ansible/modules/net_tools/basics/slurp.py
    <127.0.0.1> PUT /root/.ansible/tmp/ansible-local-24449ljfccz75/tmpdopvwfyq TO /root/.ansible/tmp/ansible-tmp-1576004604.8780084-124655683624288/AnsiballZ_slurp.py
    <127.0.0.1> EXEC /bin/sh -c 'chmod u+x /root/.ansible/tmp/ansible-tmp-1576004604.8780084-124655683624288/ /root/.ansible/tmp/ansible-tmp-1576004604.8780084-124655683624288/AnsiballZ_slurp.py && sleep 0'
    <127.0.0.1> EXEC /bin/sh -c '/usr/local/virtualenv/py3/ansible_stable/bin/python3 /root/.ansible/tmp/ansible-tmp-1576004604.8780084-124655683624288/AnsiballZ_slurp.py && sleep 0'
    <127.0.0.1> EXEC /bin/sh -c 'rm -f -r /root/.ansible/tmp/ansible-tmp-1576004604.8780084-124655683624288/ > /dev/null 2>&1 && sleep 0'
    fatal: [localhost]: FAILED! => {
        "changed": false,
        "invocation": {
            "module_args": {
                "src": "/etc/ssh/ssh_known_hosts"
            }
        },
        "msg": "file not found: /etc/ssh/ssh_known_hosts"
    }
    ...ignoring

    TASK [ssh_client : debug] *********************************************************************************************
    task path: ./roles/ssh_client/tasks/clean_known_hosts.yml:10
    skipping: [localhost] => {}

    TASK [ssh_client : Unexpected Exception] ******************************************************************************
    task path: ./roles/ssh_client/tasks/main.yml:8
    included: ./roles/ssh_client/tasks/clean_known_hosts.yml for localhost
    ERROR! Unexpected Exception, this is probably a bug: 'Block' object has no attribute 'get_search_path'
    the full traceback was:

    Traceback (most recent call last):
      File "/usr/local/virtualenv/py3/ansible_stable/bin/ansible-playbook", line 123, in <module>
        exit_code = cli.run()
      File "/usr/local/virtualenv/py3/ansible_stable/lib/python3.7/site-packages/ansible/cli/playbook.py", line 127, in run
        results = pbex.run()
      File "/usr/local/virtualenv/py3/ansible_stable/lib/python3.7/site-packages/ansible/executor/playbook_executor.py", line 169, in run
        result = self._tqm.run(play=play)
      File "/usr/local/virtualenv/py3/ansible_stable/lib/python3.7/site-packages/ansible/executor/task_queue_manager.py", line 240, in run
        play_return = strategy.run(iterator, play_context)
      File "/usr/local/virtualenv/py3/ansible_stable/lib/python3.7/site-packages/ansible/plugins/strategy/linear.py", line 367, in run
        _hosts_all=self._hosts_cache_all,
      File "/usr/local/virtualenv/py3/ansible_stable/lib/python3.7/site-packages/ansible/vars/manager.py", line 195, in get_vars
        basedirs = task.get_search_path()
    AttributeError: 'Block' object has no attribute 'get_search_path'


./ansible.cfg

    [defaults]
    playbook_vars_root = all

./example.yml

    ---
    - hosts: localhost
      gather_facts: no
      roles:
      - ssh_client

./roles/ssh_client/tasks/main.yml

    ---
    - name: No exception
      include_tasks:
        file: clean_known_hosts.yml
      vars:
        known_hosts_file: /etc/ssh/ssh_known_hosts

    - name: Unexpected Exception
      include_tasks:
        file: clean_known_hosts.yml
        apply:
          become: yes
      vars:
        known_hosts_file: /etc/ssh/ssh_known_hosts

./roles/ssh_client/tasks/clean_known_hosts.yml

    ---
    - name: Read {{ known_hosts_file }}
      slurp:
        src: "{{ known_hosts_file }}"
      register: current_known_hosts
      ignore_errors: yes

    - when: current_known_hosts is not failed
      block:
      - debug:


##### EXPECTED RESULTS

No `ERROR! Unexpected Exception`

#
#
#
#
from __future__ import (absolute_import, division, print_function)
__metaclass__ = type
DOCUMENTATION = '''
    name: free
    short_description: Executes tasks without waiting for all hosts
    description:
        - Task execution is as fast as possible per batch as defined by C(serial) (default all).
          Ansible will not wait for other hosts to finish the current task before queuing more tasks for other hosts.
          All hosts are still attempted for the current task, but it prevents blocking new tasks for hosts that have already finished.
        - With the free strategy, unlike the default linear strategy, a host that is slow or stuck on a specific task
          won't hold up the rest of the hosts and tasks.
    version_added: "2.0"
    author: Ansible Core Team
'''
import time
from ansible import constants as C
from ansible.errors import AnsibleError
from ansible.playbook.included_file import IncludedFile
from ansible.plugins.loader import action_loader
from ansible.plugins.strategy import StrategyBase
from ansible.template import Templar
from ansible.module_utils._text import to_text
from ansible.utils.display import Display
display = Display()
class StrategyModule(StrategyBase):