Win and Win x64 builders are failing on the chromium.perf waterfall

Link to buildbot status page:
Win:
https://build.chromium.org/p/chromium.perf/builders/Win%20Builder
https://build.chromium.org/p/chromium.perf/builders/Win%20Builder/builds/50301

Win X64:
https://build.chromium.org/p/chromium.perf/builders/Win%20x64%20Builder
https://build.chromium.org/p/chromium.perf/builders/Win%20x64%20Builder/builds/47793

The issue affects most windows builder slaves, although not all of them. Please let me know if you need a full list of affected slaves.


Exception:
error in RunProcess._startCommand
Traceback (most recent call last):
  File "C:\b\build\third_party\buildbot_slave_8_4\buildslave\runprocess.py", line 379, in start
    self._startCommand()
  File "C:\b\build\third_party\buildbot_slave_8_4\buildslave\runprocess.py", line 499, in _startCommand
    usePTY=self.usePTY)
  File "C:\b\build\third_party\buildbot_slave_8_4\buildslave\runprocess.py", line 525, in _spawnProcess
    path, usePTY=usePTY)
  File "C:\b\build\third_party\twisted_10_2\twisted\internet\posixbase.py", line 335, in spawnProcess
    raise NotImplementedError, "spawnProcess not available since pywin32 is not installed."
NotImplementedError: spawnProcess not available since pywin32 is not installed.