I used bazel to build Keras from source on Windows 10. I ran this command:
bazel --output_user_root=C:/tmp5 build //keras/tools/pip_package:build_pip_package
Then, when I wanted to create the package with this command:
bazel-bin\keras\tools\pip_package\build_pip_package C:/tmp/keras_pkg
I got this error:

It seems that the error came from the buil_pip_pacakge file (line 36):

I verified that the folder "bazel-bin" was created:

The following figures present the sub-elements of the folders "bazel-bin" and "build_pip_package.exe.runfiles":

