fix(python): Fix Tornado to work on win32 Python 3.8+
fix(python): Fix Tornado to work on win32 Python 3.8+

Thanks to Nila Moenig for reporting.

Fixes https://github.com/google/neuroglancer/issues/253

janelia-flyem/neuroglancer,google/neuroglancer,google/neuroglancer,google/neuroglancer,janelia-flyem/neuroglancer,google/neuroglancer,google/neuroglancer,google/neuroglancer,janelia-flyem/neuroglancer,janelia-flyem/neuroglancer,google/neuroglancer,janelia-flyem/neuroglancer,google/neuroglancer