use configobj for post-install config changes

The Python configobj library is what SABnzbd uses to create and modify
their ini config file. Figured it'd be easiest to do the same, at least
for when we need to make changes after the initial config file has been
copied.

nixarr/sabnzbd/config.nix

@@ -59,22 +59,33 @@ let
     '';
   };
 
-  apply-user-configs-script = pkgs.writeShellApplication {
-    name = "sabnzbd-set-user-values";
-    runtimeInputs = with pkgs; [gnused util-linux];
-    text = with lib; ''
-      if [ ! -f ${ini-file-target} ]; then
-        echo "FAILURE: Cannot write changes to ${ini-file-target}, file does not exist"
-        exit 1
-      fi
+  user-configs-to-python = with lib;
+    attrsets.collect (f: !builtins.isAttrs f) (
+      attrsets.mapAttrsRecursive (
+        path: value:
+          "sab_config_map['"
+          + (lib.strings.concatStringsSep "']['" path)
+          + "'] = '"
+          + (builtins.toString value)
+          + "'"
+      )
+      user-configs
+    );
+  apply-user-configs-script = with lib; (pkgs.writers.writePython3Bin
+    "sabnzbd-set-user-values" {libraries = [pkgs.python3Packages.configobj];} ''
+      from pathlib import Path
+      from configobj import ConfigObj
 
-      cp --preserve ${ini-file-target}{,.tmp}
-      < ${ini-file-target} \
-    '' + (strings.concatStringsSep "|" (lists.flatten user-config-set-cmds))
-    + ''
-      > ${ini-file-target}.tmp && mv -f ${ini-file-target}{.tmp,}
-    '';
-  };
+      sab_config_path = Path("${ini-file-target}")
+      if not sab_config_path.is_file() or sab_config_path.suffix != ".ini":
+          raise Exception(f"{sab_config_path} is not a valid config file path.")
+
+      sab_config_map = ConfigObj(str(sab_config_path))
+
+      ${lib.strings.concatStringsSep "\n" user-configs-to-python}
+
+      sab_config_map.write()
+    '');
 
   bashCheckIfEmptyStr = v: "[[ -z \$${v} || \$${v} == '\"\"' ]]";
   gen-uuids-script = pkgs.writeShellApplication {