test: Break on test script (or other) error

Break notmuch-test whenever a test script returns non-zero status.
This happens either when some test from the script fails or when there
is an error in the script.

This is especially useful in the latter case since the error may not
appear in the final aggregated results.

test/notmuch-test

@@ -14,12 +14,20 @@ if [ ${BASH_VERSINFO[0]} -lt 4 ]; then
     exit 1
 fi
 
+set -e
+
+die () {
+    echo >&2 "Unexpected failure"
+}
+
+trap 'die' 0
+
 cd $(dirname "$0")
 
 TESTS="basic new search json thread-naming raw reply dump-restore uuencode thread-order author-order from-guessing long-id encoding emacs maildir-sync"
 
 # Clean up any results from a previous run
-rm -r test-results >/dev/null 2>/dev/null
+rm -rf test-results >/dev/null 2>/dev/null
 
 # Run the tests
 for test in $TESTS; do
@@ -31,3 +39,5 @@ done
 
 # Clean up
 rm -r test-results corpus.mail
+
+trap '' 0