flake: check for existance of python project

flake.nix

@@ -28,12 +28,21 @@
                     pkgs.deno
                 ];
                 shellHook = ''
+                    if [ -f .env ]; then
+                        set -a
+                        source .env
+                        set +a
+                    fi
+
                     if [ ! -d .venv ]; then
                         echo "Creating Python virtual environment in .venv"
                         python3 -m venv .venv
                     fi
+
+                    if compgen -G "app/*.py" > /dev/null; then
                         .venv/bin/pip install -r ./app/requirements.txt
                         source .venv/bin/activate
+                    fi
                 '';
             };
         });