travis: Fail when a unit test fails

* Oops, this never actually aborted when something went wrong.
* Fix that and abort.
* Print a brief message about the last script run that blew up.

.travis.yml

@@ -18,4 +18,4 @@ before_install:
     - docker run kylemanna/openvpn openssl version
 
 script:
-    - pushd tests && for i in *.sh; do echo -e "\n\n>> Running test $i\n\n"; "./$i"; done && popd
+    - ./test-ci.sh

test-ci.sh

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+set -x
+
+cd "$(dirname "$(readlink -f "$0")")/tests"
+
+for i in *.sh; do
+    echo -e "\n>> Running test $i\n"
+    ./${i}
+    retval=$?
+    if [ $retval != 0 ]; then
+        echo "Failed $i with exit code $retval"
+        exit $retval
+    fi
+done