Handle NotFound exception when establishing trust
Establishing trust implies discovery of the trusted domain's domain controller via DNS.
If DNS discovery is not possible, NotFound exception is raised.
Intercept the exception and process it to help diagnose and fix actual problem:
- if IPA is managing DNS, suggest to make a forward for the domain's zone
- otherwise suggest to setup DNS forwarder at upstream DNS server
https://fedorahosted.org/freeipa/ticket/3103