Require setuptools>=40.8.0 (#200)

Author: bbtong

invokers/python/Dockerfile

@@ -11,7 +11,7 @@ WORKDIR /workspace/invoker
 RUN tox sdist
 RUN mkdir -p /out
 RUN cp /workspace/invoker/.tox/dist/*.tar.gz /out
-RUN pip download --no-binary 'MarkupSafe' -d /workspace/dependencies .
+RUN pip download --no-binary 'MarkupSafe' 'setuptools>=40.8.0' -d /workspace/dependencies .
 RUN tar -cvzf /out/pyfunc-invoker-deps-$(cat /workspace/invoker/VERSION).tar.gz -C /workspace/dependencies .
 
 ENTRYPOINT [ "tox" ]