使用 tox for py26 安装 pandas

Question

使用tox 为我的包运行pytest 时出现问题，使用py26 作为环境之一（全局环境是py3.6，py26 环境是通过pyenv 安装的py2.6.9）

tox.ini 文件：

[tox]
envlist = py26,py27,py36
[testenv]
deps=
   pytest
   PyPDT
   py26: numpy<1.12.0
   py{27,36}: numpy
   py26: pandas==0.16.2
   py{27,36}: pandas
   py26: matplotlib<1.5.0
   py{27,36}: matplotlib<2.1.0

commands=pytest

pandas安装时出现如下错误：

Collecting pandas==0.16.2
  Using cached pandas-0.16.2.tar.gz
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/private/var/folders/pr/ghw8lmr94c5g9ntx4cp9990w0000gn/T/pip-build-cuCAyE/pandas/setup.py", line 406, in <module>
        from wheel.bdist_wheel import bdist_wheel
      File "/Users/brianpollack/Coding/scikit-hep/.tox/py26/lib/python2.6/site-packages/wheel/bdist_wheel.py", line 407
        ignore=lambda x, y: {'PKG-INFO', 'requires.txt', 'SOURCES.txt',
                                       ^
    SyntaxError: invalid syntax

    ----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /private/var/folders/pr/ghw8lmr94c5g9ntx4cp9990w0000gn/T/pip-build-cuCAyE/pandas/

ERROR: could not install deps [setuptools, pytest, PyPDT, numpy<1.12.0, pandas==0.16.2, matplotlib<1.5.0]; v = InvocationError('/Users/brianpollack/Coding/scikit-hep/.tox/py26/bin/pip install setuptools pytest PyPDT numpy<1.12.0 pandas==0.16.2 matplotlib<1.5.0 (see /Users/brianpollack/Coding/scikit-hep/.tox/py26/log/py26-1.log)', 1)

知道是什么导致了这个语法错误吗？

编辑：

更新的最佳答案：使用-cconstraints.txt 强制执行降级版本的wheel

Answer 1

wheeldropped support for Python 2.6.

安装wheel兼容Python 2.6安装版本0.29：

source /Users/brianpollack/Coding/scikit-hep/.tox/py26/bin/activate‌​
pip uninstall wheel
pip install wheel==0.29.0

在 tox.ini 中：

[testenv]
deps=
    …
    py26: wheel==0.29.0
    …

或者试试constraints file:

[testenv]
deps=
    …
    -cconstraints.txt
    …

约束.txt：

wheel==0.29.0