def match_hostname(cert, hostname):
        """Verify that *cert* (in decoded format as returned by
        SSLSocket.getpeercert()) matches the *hostname*.  RFC 2818 and RFC 6125
        rules are followed, but IP addresses are not accepted for *hostname*.

        CertificateError is raised on failure. On success, the function
        returns nothing.
        """
        if not cert:
            raise ValueError("empty or no certificate, match_hostname needs a "
                             "SSL socket or SSL context with either "
                             "CERT_OPTIONAL or CERT_REQUIRED")
        dnsnames = []
        san = cert.get('subjectAltName', ())
        for key, value in san:
            if key == 'DNS':
                if _dnsname_match(value, hostname):
                    return
                dnsnames.append(value)
        if not dnsnames:
            # The subject is only checked when there is no dNSName entry
            # in subjectAltName
            for sub in cert.get('subject', ()):
                for key, value in sub:
                    # XXX according to RFC 2818, the most specific Common Name
                    # must be used.
                    if key == 'commonName':
                        if _dnsname_match(value, hostname):
                            return
                        dnsnames.append(value)
        if len(dnsnames) > 1:
            raise CertificateError("hostname %r "
                "doesn't match either of %s"
                % (hostname, ', '.join(map(repr, dnsnames))))
        elif len(dnsnames) == 1:
            raise CertificateError("hostname %r "
                "doesn't match %r"
                % (hostname, dnsnames[0]))
        else:
            raise CertificateError("no appropriate commonName or "
                "subjectAltName fields were found")
Verify that *cert* (in decoded format as returned by
        SSLSocket.getpeercert()) matches the *hostname*.  RFC 2818 and RFC 6125
        rules are followed, but IP addresses are not accepted for *hostname*.

        CertificateError is raised on failure. On success, the function
        returns nothing.
        
product/gradle-plugin/src/main/python/pip/_vendor/distlib/compat.py