mamba环境中Python3.6与pylint兼容问题及依赖排查求助

在Linux系统中通过mamba创建Python3.6干净环境并安装代码检查工具后，运行pylint出现兼容性报错：

操作步骤 #

mamba create -n py_36_dev_generic python=3.6
mamba activate py_36_dev_generic
mamba install pylint pycodestyle pydocstyle

报错信息 #

Traceback (most recent call last):
  File "/home/johndoe/mambaforge/envs/py_36_dev_generic/bin/pylint", line 10, in <module>
    sys.exit(run_pylint())
  File "/home/johndoe/mambaforge/envs/py_36_dev_generic/lib/python3.6/site-packages/pylint/__init__.py", line 21, in run_pylint
    from pylint.lint import Run as PylintRun
  File "/home/johndoe/mambaforge/envs/py_36_dev_generic/lib/python3.6/site-packages/pylint/lint/__init__.py", line 76, in <module>
    from pylint.lint.parallel import check_parallel
  File "/home/johndoe/mambaforge/envs/py_36_dev_generic/lib/python3.6/site-packages/pylint/lint/parallel.py", line 9, in <module>
    from pylint.lint.utils import _patch_sys_path
  File "/home/johndoe/mambaforge/envs/py_36_dev_generic/lib/python3.6/site-packages/pylint/lint/utils.py", line 10, in <module>
    from pylint.config import PYLINT_HOME
  File "/home/johndoe/mambaforge/envs/py_36_dev_generic/lib/python3.6/site-packages/pylint/config/__init__.py", line 43, in <module>
    import platformdirs
  File "/home/johndoe/mambaforge/envs/py_36_dev_generic/lib/python3.6/site-packages/platformdirs/__init__.py", line 5
    from __future__ import annotations
    ^
SyntaxError: future feature annotations is not defined

依赖排查结果 #

• 安装的pylint版本为2.11.1，依赖platformdirs >=2.2.0
• 自动安装的platformdirs版本为2.5.1，conda-forge标注其支持Python>=3.6
• 但__future__ annotations是Python3.7及以上才支持的特性，Python3.6无法识别

这确实是conda-forge仓库中platformdirs包的依赖定义bug：包的实际代码依赖Python3.7+，但包的元数据错误标注为支持Python3.6，导致mamba在Python3.6环境中安装了不兼容的版本。

直接在当前环境中安装兼容Python3.6的platformdirs版本，强制指定版本上限：

mamba install "platformdirs<=2.4.0"

安装完成后重新运行python -m pylint即可正常使用。

如果要避免后续新建环境时重复出现问题，可以在安装pylint时直接附带兼容的platformdirs版本约束：

mamba create -n py_36_dev_generic python=3.6
mamba activate py_36_dev_generic
mamba install pylint pycodestyle pydocstyle "platformdirs<=2.4.0"

内容的提问来源于stack exchange，提问作者darmual