pythonPackages.pq: fix build

we can't run the tests anyway, so remove fragile attempts to patch them

pkgs/development/python-modules/pq/default.nix

@@ -1,7 +1,6 @@
 { lib
 , buildPythonPackage
 , fetchPypi
-, psycopg2
 , isPy27
 }:
 
@@ -15,22 +14,9 @@ buildPythonPackage rec {
     sha256 = "f54143844e73f4182532e68548dee447dd78dd00310a087e8cdee756d476a173";
   };
 
-  # psycopg2cffi is compatible with psycopg2 and author states that
-  # module is compatible with psycopg2
-  postConfigure = ''
-    substituteInPlace setup.py \
-      --replace "psycopg2cffi" "psycopg2"
-
-    substituteInPlace pq/tests.py \
-      --replace "psycopg2cffi" "psycopg2"
-  '';
-
-  checkInputs = [
-    psycopg2
-  ];
-
   # tests require running postgresql cluster
   doCheck = false;
+  pythonImportsCheck = [ "pq" ];
 
   meta = with lib; {
     description = "PQ is a transactional queue for PostgreSQL";