buildPythonPackage: fix standalone applications using it

pkgs/applications/misc/pytrainer/default.nix

@@ -27,12 +27,12 @@ pythonPackages.buildPythonPackage rec {
   # string, which allows setting an explicit MIME type.
   patches = [ ./pytrainer-webkit.patch ];
 
-  pythonPath = with pythonPackages; [
+  propagatedBuildInputs = with pythonPackages; [
     dateutil lxml matplotlibGtk pyGtkGlade pywebkitgtk
-    sqlalchemy sqlalchemy_migrate
+    sqlalchemy_migrate
   ];
 
-  buildInputs = [gpsbabel sqlite] ++ pythonPath;
+  buildInputs = [ gpsbabel sqlite ];
 
   # This package contains no binaries to patch or strip.
   dontPatchELF = true;