--- a/Makefile	Tue Oct 31 12:09:26 2017 +0800
+++ b/Makefile	Tue Oct 31 12:44:53 2017 +0800
@@ -1,3 +1,10 @@
+MAKEFLAGS += --warn-undefined-variables
+SHELL := bash
+.SHELLFLAGS := -eu -o pipefail -c
+.DEFAULT_GOAL := all
+.DELETE_ON_ERROR:
+.SUFFIXES:
+
 pip := ./venv/bin/pip install -r REQUIREMENTS