travis-ci: cat output of failed tests

.ci/proveit.sh

@@ -0,0 +1,8 @@
+#!/bin/sh
+set -e
+
+if ! prove -e cat -f "$1"
+then
+  cat "$1"
+  exit 1
+fi

.ci/travis-build.sh

@@ -16,5 +16,5 @@ make -j2 $EXTRA
 if [ "$TEST" != "NO" ]
 then
   make tapfiles
-  find . -name '*.tap' -print0 | xargs -0 -n1 prove -e cat -f
+  find . -name '*.tap' -print0 | xargs -0 -n1 ./.ci/proveit.sh
 fi