title: LDAP search attributes
body: <p>I have a search on my LDAP base which is:</p>
  
  <pre><code>user_account = server.search_s(
      'ou=usuarios,ou=xxx,o=system xxx',
      ldap.SCOPE_ONELEVEL,
      'uid=' + login,
      ['uid', 'mail', 'objectClass', 'CPF'])[0]
    if user_account[1]['CPF'] is not None:
      plpy.debug("It has CPF")
  </code></pre>
  
  <p>That's working fine if the CPF field is filled, but if it's not filled it gives me an error:</p>
  
  <pre><code>ERROR:  KeyError: 'CPF'
  </code></pre>
  
  <p>I have tried to do:</p>
  
  <pre><code>if user_account[1]['CPF'] is None:
      plpy.debug("It hasn't CPF")
  </code></pre>
  
  <p>But it's giving me the same error.</p>