<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def _auth(url):
    '''
    Install an auth handler for urllib2
    '''
    user = __salt__['config.get']('solr.user', False)
    password = __salt__['config.get']('solr.passwd', False)
    realm = __salt__['config.get']('solr.auth_realm', 'Solr')

    if user and password:
        basic = _HTTPBasicAuthHandler()
        basic.add_password(
            realm=realm, uri=url, user=user, passwd=password
        )
        digest = _HTTPDigestAuthHandler()
        digest.add_password(
            realm=realm, uri=url, user=user, passwd=password
        )
        _install_opener(
            _build_opener(basic, digest)
        )