rules_python 1.7.0 (PR #3242) introduced %interpreter_args% template placeholder
in bootstrap scripts. External py_binary targets don't substitute this, causing:
File ".../cython_binary", line 39
%interpreter_args%
^
SyntaxError: invalid syntax
# 1bb07d8: rules_python 1.6.3 - WORKS
git checkout 1bb07d8
bazel build @com_github_grpc_grpc//src/python/grpcio/grpc/_cython:cygrpc.pyx_cython_translation
# 3ca4b67: rules_python 1.7.0 - FAILS
git checkout 3ca4b67
bazel clean --expunge # if needed
bazel build @com_github_grpc_grpc//src/python/grpcio/grpc/_cython:cygrpc.pyx_cython_translation