Move the error node checking to a rule.

test/failing_examples.py

@@ -137,6 +137,7 @@ FAILING_EXAMPLES = [
     'def x():\n    1\n 2',
     'def x():\n 1\n  2',
     'if 1:\nfoo',
+    'if 1: blubb\nif 1:\npass\nTrue and False',
 ]
 
 GLOBAL_NONLOCAL_ERROR = [

test/test_python_errors.py

@@ -21,6 +21,7 @@ def _get_error_list(code, version=None):
     tree = grammar.parse(code)
     return list(grammar.iter_errors(tree))
 
+
 def assert_comparison(code, error_code, positions):
     errors = [(error.start_pos, error.code) for error in _get_error_list(code)]
     assert [(pos, error_code) for pos in positions] == errors