$VIMPRG is always empty when printed, escape it to make the message actual helpful

diff --git a/test/run_tests.sh b/test/run_tests.sh
index b7bde7fb2f3426cc0c25d8de3fc5f33da550ca80..a68e0b9c826f259b0442d2fe70186c58ed9bb640 100755 (executable)
--- a/test/run_tests.sh
+++ b/test/run_tests.sh
@@ -4,7 +4,7 @@
 
 VIMPRG=${VIMPRG:=$(which vim)}
 if [ -z "$VIMPRG" ]; then
-  echo "ERROR: $VIMPRG is not found in PATH"
+  echo "ERROR: vim (\$VIMPRG) is not found in PATH"
   exit 1
 fi