dns.rdataset.DifferingCovers:
Raised if an attempt is made to add a SIG/RRSIG whose covered type
is not the same as that of the other rdatas in the rdataset.
dns.name.NeedAbsoluteNameOrOrigin:
Raised if an attempt is made to convert a non-absolute name to wire
when there is also a non-absolute (or missing) origin.
dns.rdtypes.mxbase.UncompressedMX:
Base class for rdata that is like an MX record, but whose name is
not compressed when converted to DNS wire format, and whose
digestable form is not downcased.
dns.rdtypes.nsbase.UncompressedNS:
Base class for rdata that is like an NS record, but whose name is
not compressed when convert to DNS wire format, and whose
digestable form is not downcased.