Refactor a bit for Python 2.

parso/python/normalizer.py

@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 from contextlib import contextmanager
 
 from parso.normalizer import Normalizer, NormalizerConfig, Issue
@@ -656,3 +657,6 @@ class ErrorFinder(Normalizer):
 
 class ErrorFinderConfig(NormalizerConfig):
     normalizer_class = ErrorFinder
+
+    def __init__(self, grammar):
+        self.grammar = grammar

parso/python/tree.py

@@ -99,8 +99,8 @@ class PythonMixin(object):
                     return result
         return None
 
-    def _iter_errors(self):
-        config = normalizer.ErrorFinderConfig()
+    def _iter_errors(self, grammar):
+        config = normalizer.ErrorFinderConfig(grammar)
         return self._get_normalizer_issues(config)