error was:
In --require-hashes mode, all requirements must have their versions pinned with ==. These do not:
setuptools from 04a0b689d3/setuptools-39.0.1-py2.py3-none-any.whl (md5)=ca299c7acd13a72e1171a3697f2b99bc (from protobuf==3.5.2.post1->-r ./contrib/deterministic-build/requirements.txt (line 21))
This is used to make sure we also freeze versions for
packages that will only be used on Windows or OS X, while
the freezing script is most likely only be run on Linux.
