Provide more info when crl-check fails.

[get_entries_by_nid](http://www.sourcecodebrowser.com/m2crypto/0.20.1/class_m2_crypto_1_1_x509_1_1_x509___name.html#a3a137c19c615ad9159f4b963fc25d61b) calls [__getitem__](http://www.sourcecodebrowser.com/m2crypto/0.20.1/class_m2_crypto_1_1_x509_1_1_x509___extension___stack.html#acd46c59ba0a32b5ba5f9d4915bf9f075) which gets things out of this 'stack' collection that communicates with the underlying openssl lib...