Merging TensorFlow on a system that does not have the system-enabled useflag on, but also with no numpy installed, causes TensorFlow to fail at build time, with bazel not detecting numpy and then bailing. The same goes for absl-py and protobuf-python, in this case tensorflow does build, however actually importing TF and using it from Python fails due to the missing dependencies. I would recommend moving these packages into unconditional dependencies whenever the python useflag is enabled.
Fixed in tensorflow-1.10.0
(In reply to Jason Zaman from comment #1) > Fixed in tensorflow-1.10.0 Looked at the ebuild, definitely looks fixed, thanks.