Check to see if policy exists.

    CLI Example:

    .. code-block:: bash

        salt myminion boto_iam.instance_profile_exists myiprofile

def get_policy(policy_name,
               region=None, key=None, keyid=None, profile=None):
    '''
    Check to see if policy exists.

    CLI Example:

    .. code-block:: bash

        salt myminion boto_iam.instance_profile_exists myiprofile
    '''
    conn = _get_conn(region=region, key=key, keyid=keyid, profile=profile)

    try:
        ret = conn.get_policy(_get_policy_arn(policy_name,
                            region=region, key=key, keyid=keyid, profile=profile))
        return ret.get('get_policy_response', {}).get('get_policy_result', {})
    except boto.exception.BotoServerError:
        return None