pythonPackages.lark-parser: enable majority of tests

pkgs/development/python-modules/lark-parser/default.nix

@@ -15,12 +15,11 @@ buildPythonPackage rec {
     sha256 = "1zynj09w361yvbxr4hir681dfnlq1hzniws9dzgmlkvd6jnhjgx3";
   };
 
-  checkPhase = ''
-    ${python.interpreter} -m unittest
+  # tests of Nearley support require js2py
+  preCheck = ''
+    rm -r tests/test_nearley
   '';
 
-  doCheck = false; # Requires js2py
-
   meta = {
     description = "A modern parsing library for Python, implementing Earley & LALR(1) and an easy interface";
     homepage = https://github.com/lark-parser/lark;