Mark failing tests

Lib/test/test_pep646_syntax.py

@@ -305,14 +305,14 @@ is *not* valid syntax.)
     {'args': StarredB}
 
     >>> def f3(*args: *b, arg1: int): pass
-    >>> f3.__annotations__
+    >>> f3.__annotations__ # TODO: RUSTPYTHON # doctest: +EXPECTED_FAILURE
     {'args': StarredB, 'arg1': <class 'int'>}
 
     >>> def f4(*args: *b, arg1: int = 2): pass
-    >>> f4.__annotations__
+    >>> f4.__annotations__ # TODO: RUSTPYTHON # doctest: +EXPECTED_FAILURE
     {'args': StarredB, 'arg1': <class 'int'>}
 
-    >>> def f5(*args: *b = (1,)): pass
+    >>> def f5(*args: *b = (1,)): pass # TODO: RUSTPYTHON # doctest: +EXPECTED_FAILURE
     Traceback (most recent call last):
         ...
     SyntaxError: invalid syntax
@@ -320,8 +320,17 @@ is *not* valid syntax.)
 
 __test__ = {'doctests' : doctests}
 
+EXPECTED_FAILURE = doctest.register_optionflag('EXPECTED_FAILURE') # TODO: RUSTPYTHON
+class CustomOutputChecker(doctest.OutputChecker): # TODO: RUSTPYTHON
+    def check_output(self, want, got, optionflags): # TODO: RUSTPYTHON
+        if optionflags & EXPECTED_FAILURE: # TODO: RUSTPYTHON
+            if want == got: # TODO: RUSTPYTHON
+                return False # TODO: RUSTPYTHON
+            return True # TODO: RUSTPYTHON
+        return super().check_output(want, got, optionflags) # TODO: RUSTPYTHON
+
 def load_tests(loader, tests, pattern):
-    tests.addTest(doctest.DocTestSuite())
+    tests.addTest(doctest.DocTestSuite(checker=CustomOutputChecker())) # TODO: RUSTPYTHON
     return tests