From: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
Date: Mon, 19 Oct 2015 21:13:43 -0400
Subject: let a failed diff be verbose

there is no reason to pass -q to diff when comparing output: if diff
succeeds, it will be quiet.  If it fails, the test fails, and so we
want it in our stderr!
---
 test/runtests | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/runtests b/test/runtests
index 43f2560..470499b 100755
--- a/test/runtests
+++ b/test/runtests
@@ -202,7 +202,7 @@ kill_by_pidfile "${sleep_pidfile}"
 unset sleep_pidfile
 
 if [ -e ${t}/output ] ; then
-    diff_output_filter_headers "${t}/output" "$output" "-q"
+    diff_output_filter_headers "${t}/output" "$output" >&2
 fi
 if [ -n "${USE_MSVA}" ]; then
     trap stop_msva EXIT