parsimonious: excluding unpredictable tests

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

@@ -17,6 +17,9 @@ buildPythonPackage rec {
   checkInputs = [ nose ];
   propagatedBuildInputs = [ six ];
 
+  # performance tests tend to fail sometimes
+  NOSE_EXCLUDE = "test_benchmarks";
+
   meta = with stdenv.lib; {
     homepage = "https://github.com/erikrose/parsimonious";
     description = "Fast arbitrary-lookahead parser written in pure Python";