Add flake as venv replacement

flake.nix

@@ -0,0 +1,15 @@
+{
+  outputs = { self, nixpkgs }:
+    let forAllSystems = nixpkgs.lib.genAttrs nixpkgs.lib.systems.flakeExposed;
+    in {
+      devShells = forAllSystems (system:
+        let
+          pkgs = import nixpkgs { inherit system; };
+          pythonPkgs = ps: with ps; [ requests ];
+        in
+        {
+          default = (pkgs.python3.withPackages pythonPkgs).env;
+        }
+      );
+    };
+}