Collect all the sys.doc output from each minion and return the aggregate

    CLI Example:

    .. code-block:: bash

        salt-run doc.execution

def execution():
    '''
    Collect all the sys.doc output from each minion and return the aggregate

    CLI Example:

    .. code-block:: bash

        salt-run doc.execution
    '''
    client = salt.client.get_local_client(__opts__['conf_file'])

    docs = {}
    try:
        for ret in client.cmd_iter('*', 'sys.doc', timeout=__opts__['timeout']):
            for v in six.itervalues(ret):
                docs.update(v)
    except SaltClientError as exc:
        print(exc)
        return []

    i = itertools.chain.from_iterable([six.iteritems(docs['ret'])])
    ret = dict(list(i))

    return ret