Function crls 

pub fn crls(
    rd: &mut dyn BufRead,
) -> impl Iterator<Item = Result<CertificateRevocationListDer<'static>, Error>>

Available on (crate features rustls or boring or acme) and crate feature rustls and crate feature std only.

Return an iterator certificate revocation lists (CRLs) from rd.

Filters out any PEM sections that are not CRLs and yields errors if a problem occurs while trying to extract a CRL.