Try to print MTA-STS missing DNS policy error reason

[ValdikSS]

When proper (not self-signed) TLS certificate is not provisioned on the domain yet, MiaB prints only:

MTA-STS policy is missing: STSFetchResult.NONE

which may confuse the administrator, as .well-known/mta-sts.txt file is already present and opens correctly.

Print more human-friendly reason for this case. Code taken from dns-update.py and slightly edited.

[JoshData]

Thanks for this. If the cert is missing or invalid, I think we can just skip the MTA-STS message entirely, since there will be a message about the certificate.

[ValdikSS]

Like this I guess? Please check.

[ValdikSS]

@JoshData, hello, any chance to get this merged?