uwsgi: fix pythonpath

pkgs/e11sync-backend.nix

@@ -13,16 +13,18 @@
   geoip-mmdb,
 }: let
   uwsgi-python = uwsgi.override {plugins = ["python3"];};
+  pythonEnv =
+    python3.withPackages
+    (ps: [
+      ps.django
+      ps.django-compressor
+      ps.geoip2
+    ]);
 in
   stdenv.mkDerivation {
     name = "e11sync-backend";
     propagatedBuildInputs = [
-      (python3.withPackages
-        (ps: [
-          ps.django
-          ps.django-compressor
-          ps.geoip2
-        ]))
+      pythonEnv
       libmaxminddb
     ];
     nativeBuildInputs = [makeWrapper];
@@ -41,6 +43,7 @@ in
         --chdir $out/app \
         --set-default E11SYNC_HTTP_PORT ${toString backendPort} \
         --add-flags "--plugin ${uwsgi-python}/lib/uwsgi/python3_plugin.so" \
+        --add-flags "--python-path ${pythonEnv}/lib/${pythonEnv.libPrefix}/site-packages" \
         --add-flags "--http-socket 127.0.0.1:${toString backendPort}" \
         --add-flags "--wsgi-file e11sync/wsgi.py" \
         --add-flags --master \