This was a regression due to a commit made less than 2 days ago.

make: [build_pywin32] running 'F:\as\apy\build\pyhg_trunk-win64-x64-hgtip27-rrun
\python\PCbuild\amd64\python.exe setup.py build' in 'build\pyhg_trunk-win64-x64-
hgtip27-rrun\pywin32'
Traceback (most recent call last):
  File "setup.py", line 83, in <module>
    from distutils.command.build_ext import build_ext
  File "F:\as\apy\build\pyhg_trunk-win64-x64-hgtip27-rrun\python\lib\distutils\c
ommand\build_ext.py", line 23, in <module>
    from distutils.msvccompiler import get_build_version
  File "F:\as\apy\build\pyhg_trunk-win64-x64-hgtip27-rrun\python\lib\distutils\m
svccompiler.py", line 657, in <module>
    from distutils.msvc9compiler import MSVCCompiler
  File "F:\as\apy\build\pyhg_trunk-win64-x64-hgtip27-rrun\python\lib\distutils\m
svc9compiler.py", line 18, in <module>
    import subprocess
  File "F:\as\apy\build\pyhg_trunk-win64-x64-hgtip27-rrun\python\lib\subprocess.
py", line 611, in <module>
    class Popen(object):
  File "F:\as\apy\build\pyhg_trunk-win64-x64-hgtip27-rrun\python\lib\subprocess.
py", line 911, in Popen
    _WaitForSingleObject=WaitForSingleObject,
NameError: name 'WaitForSingleObject' is not defined