Add default.nix, allow for nix run.

default.nix

@@ -0,0 +1,12 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+with pkgs.python3Packages;
+buildPythonPackage rec {
+    name = "hb-downloader";
+    src = ./.;
+    propagatedBuildInputs = [ requests pkgs.aria2 ];
+    meta.mainProgram = "hb-downloader";
+    postInstall = ''
+        mv -v $out/bin/hb-downloader.py $out/bin/hb-downloader
+    '';
+}

flake.nix

@@ -11,5 +11,6 @@
         in
         {
             devShells.x86_64-linux.default = ( import ./shell.nix { inherit pkgs; });
+            packages.x86_64-linux.default = ( import ./default.nix { inherit pkgs; });
         };
 }

requirements.txt

@@ -0,0 +1 @@
+requests

setup.py

@@ -0,0 +1,11 @@
+from setuptools import setup
+
+with open('requirements.txt') as f:
+    install_requires = f.read().splitlines()
+
+setup(
+        name = 'hb-downloader',
+        version = '0.1',
+        install_requires=install_requires,
+        scripts=['hb-downloader.py',],
+)