grep -P, it seems

tests/test_versions/test.sh

@@ -10,7 +10,7 @@ if which ack &>/dev/null; then
   __SEARCH_COMMAND__="ack --passthru"
 else
   echo "ack is not installed; defaulting to grep, but note that the log will be missing the IOC log" >&2
-  __SEARCH_COMMAND__="grep -E"
+  __SEARCH_COMMAND__="grep -P"
 fi
 
 function usage {