在遵循MacOS安装并成功运行.configuration脚本之后，尝试构建pip包时出错。终端中的错误显示如下：
Sat Nov 25 22:47:25 EST 2017 : === Building wheel
error in tensorflow setup command: 'install_requires' must be a string or list of strings containing valid project/version requirement specifiers; Expected ',' or end-of-list in backports.weakref >= 1.0rc1; python_version < "3.4" at ; python_version < "3.4"
完整的错误消息是：
Laurences-MacBook-Pro-3:tensorflow qaneuro$ bazel-bin/tensorflow/tools/pip_package/build_pip_package /tmp/tensorflow_pkg
Sat Nov 25 22:47:21 EST 2017 : === Using tmpdir: /var/folders/7t/77lrlr0n56z9s05dbzl42lq00000gn/T/tmp.XXXXXXXXXX.1suikQIy
~/ex5/tensorflow/bazel-bin/tensorflow/tools/pip_package/build_pip_package.runfiles ~/ex5/tensorflow
~/ex5/tensorflow
/var/folders/7t/77lrlr0n56z9s05dbzl42lq00000gn/T/tmp.XXXXXXXXXX.1suikQIy ~/ex5/tensorflow
Sat Nov 25 22:47:25 EST 2017 : === Building wheel
error in tensorflow setup command: 'install_requires' must be a string or list of strings containing valid project/version requirement specifiers; Expected ',' or end-of-list in backports.weakref >= 1.0rc1; python_version < "3.4" at ; python_version < "3.4"
是否有其他人遇到过这个问题，或者可以就如何解决这个问题提供建议？