use EnvironmentFile in dyndns systemd service to drastically uncomplicate things

nixos/server/dyndns/default.nix

@@ -3,12 +3,7 @@
   ...
 }:
 let
-  pyenv = pkgs.python3.withPackages (
-    ps: with ps; [
-      nc-dnsapi
-      python-dotenv
-    ]
-  );
+  pyenv = pkgs.python3.withPackages (ps: with ps; [ nc-dnsapi ]);
 in
 {
   users.groups.dyndns = { };
@@ -32,7 +27,8 @@ in
     serviceConfig = {
       Type = "oneshot";
       User = "dyndns";
-      ExecStart = "${pyenv.interpreter} ${./dyndns.py} ${./nc.env.secret}";
+      ExecStart = "${pyenv.interpreter} ${./dyndns.py}";
+      EnvironmentFile = ./. + "/nc.env.secret";
     };
   };
 }

nixos/server/dyndns/dyndns.py

@@ -1,17 +1,10 @@
 from nc_dnsapi import Client
-from dotenv import dotenv_values
-import sys, urllib3
+import os, urllib3
 
-if len(sys.argv) != 2:
-    raise Exception("Something funky is going on with argv")
-
-dotenv_path = sys.argv[1]
-secrets = dotenv_values(dotenv_path)
-
-CUSTOMER = secrets["NC_CUSTOMER"]
-API_PASSWORD = secrets["NC_API_PASSWORD"]
-API_KEY = secrets["NC_API_KEY"]
-DOMAIN = secrets["NC_DOMAIN"]
+CUSTOMER = os.environ["NC_CUSTOMER"]
+API_PASSWORD = os.environ["NC_API_PASSWORD"]
+API_KEY = os.environ["NC_API_KEY"]
+DOMAIN = os.environ["NC_DOMAIN"]
 
 ip = urllib3.request("GET", "https://api.ipify.org").data.decode()