Add user to group.

    .. versionadded:: 2015.8.0

    CLI Example:

    .. code-block:: bash

        salt myminion boto_iam.add_user_to_group myuser mygroup

def add_user_to_group(user_name, group_name, region=None, key=None, keyid=None,
                      profile=None):
    '''
    Add user to group.

    .. versionadded:: 2015.8.0

    CLI Example:

    .. code-block:: bash

        salt myminion boto_iam.add_user_to_group myuser mygroup
    '''
    user = get_user(user_name, region, key, keyid, profile)
    if not user:
        log.error('Username : %s does not exist.', user_name)
        return False
    if user_exists_in_group(user_name, group_name, region=region, key=key,
                            keyid=keyid, profile=profile):
        return True
    conn = _get_conn(region=region, key=key, keyid=keyid, profile=profile)
    try:
        info = conn.add_user_to_group(group_name, user_name)
        if not info:
            return False
        return info
    except boto.exception.BotoServerError as e:
        log.debug(e)
        log.error('Failed to add IAM user %s to group %s.', user_name, group_name)
        return False