All the stable 3.x Windows buildbots are failing since (https://github.com/python/cpython/pull/14139) was merged:

https://buildbot.python.org/all/#/builders/3/builds/3026
https://buildbot.python.org/all/#/builders/40/builds/2621
https://buildbot.python.org/all/#/builders/12/builds/2766

Extract from the logs:

2 tests failed:
    test_asdl_parser test_clinic

 ======================================================================
ERROR: test_attributes (test.test_asdl_parser.TestAsdlParser)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "D:\buildarea\3.x.bolen-windows10\build\lib\test\test_asdl_parser.py", line 64, in test_attributes
    stmt = self.types['stmt']
KeyError: 'stmt'
======================================================================
ERROR: test_constructor_fields (test.test_asdl_parser.TestAsdlParser)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "D:\buildarea\3.x.bolen-windows10\build\lib\test\test_asdl_parser.py", line 72, in test_constructor_fields
    ehandler = self.types['excepthandler']
KeyError: 'excepthandler'
======================================================================
ERROR: test_definitions (test.test_asdl_parser.TestAsdlParser)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "D:\buildarea\3.x.bolen-windows10\build\lib\test\test_asdl_parser.py", line 54, in test_definitions
    self.assertIsInstance(self.types['withitem'], self.asdl.Product)
KeyError: 'withitem'
======================================================================
ERROR: test_product (test.test_asdl_parser.TestAsdlParser)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "D:\buildarea\3.x.bolen-windows10\build\lib\test\test_asdl_parser.py", line 58, in test_product
    alias = self.types['alias']
KeyError: 'alias'
======================================================================
ERROR: test_visitor (test.test_asdl_parser.TestAsdlParser)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "D:\buildarea\3.x.bolen-windows10\build\lib\test\test_asdl_parser.py", line 119, in test_visitor
    v.visit(self.types['mod'])
KeyError: 'mod'
======================================================================
FAIL: test_module (test.test_asdl_parser.TestAsdlParser)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "D:\buildarea\3.x.bolen-windows10\build\lib\test\test_asdl_parser.py", line 45, in test_module
    self.assertIn('stmt', self.types)
AssertionError: 'stmt' not found in {Sum([Construct....
----------------------------------------------------------------------

I cannot reproduce the error locally on my Windows 10 machine, but it fails consistently. I made a custom run in one of the buildbots and still fails:

https://buildbot.python.org/all/#/builders/3/builds/3027