ess due to an expired or
invalidated access token.</p>

<p>In the case of OAuth2, this method would use the refresh token of the <code><a href="../Protocols/Authenticator.html#/s:9Alamofire13AuthenticatorP10CredentialQa">Credential</a></code> to generate a new
<code><a href="../Protocols/Authenticator.html#/s:9Alamofire13AuthenticatorP10CredentialQa">Credential</a></code> using the authentication service. Once complete, the <code>completion</code> closure should be called with
the new <code><a href="../Prot