Why does OSX fail on parsing the extras_require section of my setup.py file?

Question

In my setup.py file, I have the following:

setup(
    ...
    extras_require={
        ':python_version<="2.7"': [
            'pydot>1.0',
            ],
        ':python_version>="3.5"': [
            'pydot3k',
            ],
    ...
)

This works fine on Linux (on Travis CI) and Windows (on AppVeyor) but fails on OSX (also on Travis) with the error message:

error in mypackage setup command: Invalid environment marker: python_version<="2.7"

What is the reason for this failure, and how can I avoid it?

Answer 1

通过在我的.travis.yml文件中添加- pip install --upgrade setuptools解决了该问题。