python3Packages.pyserial-asyncio: propagate pyserial

Fixes errors like this:

ERROR: Could not find a version that satisfies the requirement pyserial (from pyserial-asyncio>=0.4->pysml==0.0.2) (from versions: none)

pkgs/development/python-modules/pyserial-asyncio/default.nix

@@ -7,13 +7,13 @@ buildPythonPackage rec {
 
   disabled = !isPy3k; # Doesn't support python older than 3.4
 
-  buildInputs = [ pyserial ];
-
   src = fetchPypi {
     inherit pname version;
     sha256 = "1vlsb0d03krxlj7vpvyhpinnyxyy8s3lk5rs8ba2932dhyl7f1n4";
   };
 
+  propagatedBuildInputs = [ pyserial ];
+
   meta = with stdenv.lib; {
     description = "asyncio extension package for pyserial";
     homepage = "https://github.com/pyserial/pyserial-asyncio";