provider/avahi_client: better error message

Change-Id: I1b44fef9b3fd5f2a6b0c5c639d07aee0f497466f
Reviewed-on: https://weave-review.googlesource.com/2251
Reviewed-by: Jacob Marble <jacobmarble@google.com>
Reviewed-by: Vitaly Buka <vitalybuka@google.com>

examples/provider/avahi_client.cc

diff --git a/examples/provider/avahi_client.cc b/examples/provider/avahi_client.cc
index 18ad555..27fae10 100644
--- a/examples/provider/avahi_client.cc
+++ b/examples/provider/avahi_client.cc
@@ -35,7 +35,8 @@
   int ret = 0;
   client_.reset(avahi_client_new(avahi_threaded_poll_get(thread_pool_.get()),
                                  {}, nullptr, this, &ret));
-  CHECK(client_) << avahi_strerror(ret);
+  CHECK(client_) << "failed to connect to avahi-daemon: "
+                 << avahi_strerror(ret);
 
   avahi_threaded_poll_start(thread_pool_.get());