Add Makefile

I don't remember if it's normal for `pytest` to fail to find the module and `python -m pytest` to succeed, but it seems like something to write down, and a Makefile is the place

Makefile

@@ -0,0 +1,7 @@
+.PHONY: *
+
+help: ## display this help
+	@awk 'BEGIN{FS = ":.*##"; printf "\033[1m\nUsage\n \033[1;92m make\033[0;36m <target>\033[0m\n"} /^[a-zA-Z0-9_-]+:.*?##/ { printf "  \033[36m%-15s\033[0m %s\n", $$1, $$2 } ' $(MAKEFILE_LIST)
+
+test: ## run pytest
+	python -m pytest

flake.nix

@@ -56,6 +56,7 @@
           pkgs.mkShell {
             packages = [
               pythonEnv
+              pkgs.gnumake
               pkgs.nixos-shell
               # We only take this dependency for htpasswd, which is a little unfortunate
               pkgs.apacheHttpd