debian/rules: show testsuite.log when tests are failing

Change-Id: Ic3322e3931612f2153797331b02f2789490e5e2b
diff --git a/debian/rules b/debian/rules
index cec3c9f..10ba659 100755
--- a/debian/rules
+++ b/debian/rules
@@ -21,3 +21,6 @@
 override_dh_clean:
 	dh_clean
 	rm -f tests/package.m4 tests/testsuite .version .tarball-version
+
+override_dh_auto_test:
+	dh_auto_test || (find . -name testsuite.log -exec cat {} \; ; false)