more_itertools throws SyntaxError when pytest installed via setuptools

[dzieciou]

I have the following minimal setup.py:

    import setuptools
    
    setuptools.setup(
        setup_requires=['pytest-runner'],
        tests_require=['mock', 'pytest'],
        test_suite='tests',
        python_requires='>=2.7',
    )

when running it with

    python setup.py test

I keep getting the following error:

Traceback (most recent call last):   File "setup.py", line 8, in

    <module>
        python_requires='>=2.7',   File "/Users/project/tmp/env/lib/python2.7/site-packages/setuptools/__init__.py",
    line 145, in setup
        return distutils.core.setup(**attrs)   File "/usr/local/Cellar/python@2/2.7.15_1/Frameworks/Python.framework/Versions/2.7/lib/python2.7/distutils/core.py",
    line 151, in setup
        dist.run_commands()   File "/usr/local/Cellar/python@2/2.7.15_1/Frameworks/Python.framework/Versions/2.7/lib/python2.7/distutils/dist.py",
    line 953, in run_commands
        self.run_command(cmd)   File "/usr/local/Cellar/python@2/2.7.15_1/Frameworks/Python.framework/Versions/2.7/lib/python2.7/distutils/dist.py",
    line 972, in run_command
        cmd_obj.run()   File "/Users/project/tmp/.eggs/pytest_runner-4.2-py2.7.egg/ptr.py",
    line 176, in run
        return self.run_tests()   File "/Users/project/tmp/.eggs/pytest_runner-4.2-py2.7.egg/ptr.py",
    line 187, in run_tests
        result_code = __import__('pytest').main()   File "/Users/project/tmp/.eggs/pytest-4.2.0-py2.7.egg/pytest.py",
    line 14, in <module>
        from _pytest.fixtures import fillfixtures as _fillfuncargs   File "/Users/project/tmp/.eggs/pytest-4.2.0-py2.7.egg/_pytest/fixtures.py",
    line 16, in <module>
        from more_itertools import flatten   File "build/bdist.macosx-10.13-x86_64/egg/more_itertools/__init__.py", line
    1, in <module  File
    "/Users/project/tmp/.eggs/more_itertools-6.0.0-py2.7.egg/more_itertools/more.py",
    line 329
        def _collate(*iterables, key=lambda a: a, reverse=False):
                                   ^ SyntaxError: invalid syntax

The problem appears also in the tests of more_itertools that are executed during first run, when setup tools installs test dependencies:

    Downloading
    https://files.pythonhosted.org/packages/dd/f4/cdfbb6f07f767e0cd8a11b16adfecc735b6eb87dbebda026ce8898e1cc22/more-itertools-6.0.0.tar.gz#sha256=590044e3942351a1bdb1de960b739ff4ce277960f2425ad4509446dbace8d9d1
    Best match: more-itertools 6.0.0 Processing
    more-itertools-6.0.0.tar.gz Writing
    /var/folders/lq/c1ll7pqx7rb28p7m_8wz3h2d0r0mws/T/easy_install-Auek5Z/more-itertools-6.0.0/setup.cfg
    Running more-itertools-6.0.0/setup.py -q bdist_egg --dist-dir
    /var/folders/lq/c1ll7pqx7rb28p7m_8wz3h2d0r0mws/T/easy_install-Auek5Z/more-itertools-6.0.0/egg-dist-tmp-I3ic_t
    warning: no files found matching 'fabfile.py'   File
    "build/bdist.macosx-10.13-x86_64/egg/more_itertools/tests/test_more.py",
    line 892
        print(item, file=f)
                        ^ SyntaxError: invalid syntax
    
      File "build/bdist.macosx-10.13-x86_64/egg/more_itertools/more.py",
    line 329
        def _collate(*iterables, key=lambda a: a, reverse=False):
                                   ^ SyntaxError: invalid syntax
    
    zip_safe flag not set; analyzing archive contents... Copying
    more_itertools-6.0.0-py2.7.egg to /Users/project/tmp/.eggs
    
    Installed /Users/project/tmp/.eggs/more_itertools-6.0.0-py2.7.egg

The problem does not happen when I install more_itertools with

    pip install more_itertools

My environment

(env) MBP-OK-32:tmp maciej.gawinecki$ pip list
Package    Version
---------- -------
pip        19.0.2
setuptools 40.8.0
wheel      0.33.0
(env) MBP-OK-32:tmp maciej.gawinecki$ Python --version
Python 2.7.15

MacOS HighSierra version 10.13.6

[michel-iamit]

Note: when I pin more-itertools to 5.0.0. the problem is 'solved': more-itertools = 5.0.0 So either fix this bug, or pin it in the requirements <= 5.0.0 (last is not prefered, but solves it for now).

[dzieciou]

@iamIT Right. Thank you!

tests_require=['mock', 'pytest','more-itertools<=5.0.0'],

solved the problem. Coming from a Java/Maven work to Python, to me looks like dependency conlflict resolution. Or it is rather a workaround for a bug in pytest?

[sambrightman]

more_itertools 6.0.0 dropped support for Python 2.7.

[nicoddemus]

Hi everyone, thanks for opening this issue.

I'm closing this as a duplicate of #4770 so we can focus the discussion there. Thanks!