The errors noticed while verifying
GDtlsConnection:peer-certificate. Normally this should be 0, but
it may not be if
GDtlsClientConnection:validation-flags is not
G_TLS_CERTIFICATE_VALIDATE_ALL, or if
GDtlsConnection::accept-certificate overrode the default behavior.
GLib guarantees that if certificate verification fails, at least
one error will be set, but it does not guarantee that all possible
errors will be set. Accordingly, you may not safely decide to
ignore any particular type of error. For example, it would be
incorrect to mask
G_TLS_CERTIFICATE_EXPIRED if you want to allow
expired certificates, because this could potentially be the only
error flag set even if other problems exist with the certificate.