style(expect): normalize debugging messages

A minor style cleanup to the messages printed by the Expect scripts to
make them a bit more consistent and descriptive.

Signed-off-by: Chris Kay <chris.kay@arm.com>
Change-Id: Ibd8ccb4423bd5aaeffc99c2f3602123794dc6200
diff --git a/expect/handle-arguments.inc b/expect/handle-arguments.inc
index 1fe03d5..83d067f 100644
--- a/expect/handle-arguments.inc
+++ b/expect/handle-arguments.inc
@@ -23,12 +23,12 @@
 }
 
 trap {
-    puts "<<test not yet complete, ignoring SIGINT>>"
+    message "test not yet complete, ignoring SIGINT"
 } SIGINT
 
 expect_after {
     eof {
-        puts "<<stream closed prematurely, exiting>>"
+        message "stream closed prematurely, exiting"
         exit -1
     }