Exercise the endpoint discovery code a little.
diff --git a/endpoint_search.go b/endpoint_search.go
index eea89e8..7611f19 100644
--- a/endpoint_search.go
+++ b/endpoint_search.go
@@ -3,6 +3,9 @@
 import "errors"
 
 var (
+	// ErrServiceNotFound is returned when no service matches the EndpointOpts.
+	ErrServiceNotFound = errors.New("No suitable service could be found in the service catalog.")
+
 	// ErrEndpointNotFound is returned when no available endpoints match the provided EndpointOpts.
 	ErrEndpointNotFound = errors.New("No suitable endpoint could be found in the service catalog.")
 )