fails:OpenSSL::X509::Certificate#public_key raises OpenSSL::X509::CertificateError by default
fails:OpenSSL::X509::Certificate#public_key returns the public_key
fails:OpenSSL::X509::Certificate#public_key= raises TypeError if argument is nil
fails:OpenSSL::X509::Certificate#public_key= raises TypeError if argument is not a OpenSSL::PKey::PKey
fails:"OpenSSL::X509::Certificate#public_key raises OpenSSL::X509::CertificateError by default"
fails:"OpenSSL::X509::Certificate#public_key returns the public_key"
fails:"OpenSSL::X509::Certificate#public_key= raises TypeError if argument is nil"
fails:"OpenSSL::X509::Certificate#public_key= raises TypeError if argument is not a OpenSSL::PKey::PKey"
