[Swan-dev] fixing confusing message

[D. Hugh Redelmeier]

I'm looking at ikev2-18-x509-alias/OUTPUT/east.pluto.log because it has

EXPECTATION FAILED at /source/programs/pluto/initiate.c:1450: c->host_pair != NULL


I see a preceding diagnostic that looks funny:

  failed to convert '192.1.2.23' at load time: does not look numeric and name lookup failed (no validation performed)

It sure does look numeric to me.  But the issue is that an IPv6
address is required.

I've been hacking on the code so that this message is now:

  failed to convert '192.1.2.23' at load time: not numeric IPv6 address and name lookup failed (no validation performed)
(I'll try to remember to fix the grammar.)

- the code is tricky and crucial so I'm going to test before I commit
  (imagine that!)

- this message implies a configuration error in the test.

- PLEASE DON'T FIX the configuration error yet.  I want to still be able
  to provoke the EXPECTATION FAILED.