Add Paths as first-class types in configs.

scripts/slave/unittests/recipe_configs_test.py

Index: scripts/slave/unittests/recipe_configs_test.py
diff --git a/scripts/slave/unittests/recipe_configs_test.py b/scripts/slave/unittests/recipe_configs_test.py
index a56258cc00dd9d7bd0cdb83fda884ae23393be9d..8492e07f46330af594772429e6dc366beffcd6d6 100755
--- a/scripts/slave/unittests/recipe_configs_test.py
+++ b/scripts/slave/unittests/recipe_configs_test.py
@@ -25,6 +25,7 @@ import test_env  # pylint: disable=W0611,F0401
 
 from slave import recipe_loader
 from slave import recipe_util
+from slave import recipe_config_types
 
 import coverage
 
@@ -100,7 +101,8 @@ def train_from_tests(args):
     if configuration_results:
       print 'Writing', file_name
       with open(file_name, 'wb') as f:
-        json.dump(configuration_results, f, sort_keys=True, indent=2)
+        json.dump(configuration_results, f, sort_keys=True, indent=2,
+                  default=recipe_config_types.json_fixup)
     else:
       print 'Empty', file_name
 
@@ -131,6 +133,9 @@ def load_tests(loader, _standard_tests, _pattern):
       def add_test_methods(cls):
         for name, result in configuration_results.iteritems():
           def add_test(name, result, expected_result):
+            # Roundtrip json to get same string encoding as load
+            result = json.loads(
+              json.dumps(result, default=recipe_config_types.json_fixup))
             def test_(self):
               self.assertEqual(result, expected_result)
             test_.__name__ += name