如何修复Python 2.7环境下Docker构建时的setup.py egg_info错误

问题 #

接手一套Docker容器化部署环境，原维护人员已离职。构建镜像时，requirements.txt中指定的包安装失败。

原requirements.txt内容 #

setuptools==40.6.3
pip==1.5.4
paramiko==2.4.2
scp==0.13.0
timeout_decorator==0.4.1
requests==2.21.0
pylint==1.9.4
jsonschema==2.6.0
six==1.11.0
dnslib==0.9.10
SQLAlchemy==1.3.5
psycopg2==2.8.3
future==0.17.1
tenacity

安装错误日志 #

Collecting lazy-object-proxy (from astroid<2.0,>=1.6->pylint==1.9.4->-r requirements.txt (line 7))
    Downloading https://files.pythonhosted.org/packages/6f/3e/7c80e8536b9d5eb66e784fff4c359adf9e55b37460fd6928192256ba71f2/lazy-object-proxy-1.7.0.tar.gz (42kB)
      Complete output from command python setup.py egg_info:
      Traceback (most recent call last):
        File "<string>", line 1, in <module>
        File "/tmp/pip-build-JMyxNe/lazy-object-proxy/setup.py", line 146, in <module>
          distclass=BinaryDistribution,
        File "/usr/lib/python2.7/dist-packages/setuptools/__init__.py", line 128, in setup
          _install_setup_requires(attrs)
        File "/usr/lib/python2.7/dist-packages/setuptools/__init__.py", line 123, in _install_setup_requires
          dist.fetch_build_eggs(dist.setup_requires)
        File "/usr/lib/python2.7/dist-packages/setuptools/dist.py", line 513, in fetch_build_eggs
          replace_conflicting=True,
        File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 774, in resolve
          replace_conflicting=replace_conflicting
        File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 1057, in best_match
          return self.obtain(req, installer)
        File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 1069, in obtain
          return installer(requirement)
        File "/usr/lib/python2.7/dist-packages/setuptools/dist.py", line 580, in fetch_build_egg
          return cmd.easy_install(req)
        File "/usr/lib/python2.7/dist-packages/setuptools/command/easy_install.py", line 698, in easy_install
          return self.install_item(spec, dist.location, tmpdir, deps)
        File "/usr/lib/python2.7/dist-packages/setuptools/command/easy_install.py", line 724, in install_item
          dists = self.install_eggs(spec, download, tmpdir)
        File "/usr/lib/python2.7/dist-packages/setuptools/command/easy_install.py", line 909, in install_eggs
          return self.build_and_install(setup_script, setup_base)
        File "/usr/lib/python2.7/dist-packages/setuptools/command/easy_install.py", line 1177, in build_and_install
          self.run_setup(setup_script, setup_base, args)
        File "/usr/lib/python2.7/dist-packages/setuptools/command/easy_install.py", line 1163, in run_setup
          run_setup(setup_script, args)
        File "/usr/lib/python2.7/dist-packages/setuptools/sandbox.py", line 253, in run_setup
          raise
        File "/usr/lib/python2.7/contextlib.py", line 35, in __exit__
          self.gen.throw(type, value, traceback)
        File "/usr/lib/python2.7/dist-packages/setuptools/sandbox.py", line 195, in setup_context
          yield
        File "/usr/lib/python2.7/contextlib.py", line 35, in __exit__
          self.gen.throw(type, value, traceback)
        File "/usr/lib/python2.7/dist-packages/setuptools/sandbox.py", line 166, in save_modules
          saved_exc.resume()
        File "/usr/lib/python2.7/dist-packages/setuptools/sandbox.py", line 141, in resume
          six.reraise(type, exc, self._tb)
        File "/usr/lib/python2.7/dist-packages/setuptools/sandbox.py", line 154, in save_modules
          yield saved
        File "/usr/lib/python2.7/dist-packages/setuptools/sandbox.py", line 195, in setup_context
          yield
        File "/usr/lib/python2.7/dist-packages/setuptools/sandbox.py", line 250, in run_setup
          _execfile(setup_script, ns)
        File "/usr/lib/python2.7/dist-packages/setuptools/sandbox.py", line 44, in _execfile
          code = compile(script, filename, 'exec')
        File "/tmp/easy_install-bKS9kl/setuptools_scm-7.0.5/setup.py", line 20
          def scm_version() -> str:
                            ^
      SyntaxError: invalid syntax

----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-build-JMyxNe/lazy-object-proxy/

已知当前使用Python 2.7（暂无法升级到Python 3+），原本这些包版本适配Python 2.7且之前运行正常，删除镜像后出现该问题，求修复方案。

解决方案 #

问题根源是：lazy-object-proxy默认拉取了不兼容Python 2.7的新版本，且依赖的setuptools_scm 7.x版本使用了Python 3的类型注解语法，导致Python 2.7解析报错。同时原requirements.txt中tenacity未指定版本，也可能拉取到不兼容版本。

按以下步骤修复：

1. 锁定所有依赖的兼容版本 #

修改requirements.txt，明确指定Python 2.7兼容的依赖版本，包括间接依赖：

setuptools==40.6.3
pip==1.5.4
paramiko==2.4.2
scp==0.13.0
timeout_decorator==0.4.1
requests==2.21.0
pylint==1.9.4
jsonschema==2.6.0
six==1.11.0
dnslib==0.9.10
SQLAlchemy==1.3.5
psycopg2==2.8.3
future==0.17.1
# 指定tenacity兼容Python2.7的最高版本
tenacity==5.1.5
# 锁定lazy-object-proxy的Python2.7兼容版本
lazy-object-proxy==1.4.3
# 锁定astroid版本（pylint的依赖，确保兼容）
astroid==1.6.6
# 锁定setuptools_scm的Python2.7兼容版本
setuptools_scm==1.19.0

2. 调整Docker构建时的pip安装命令 #

在Dockerfile中，使用pip install时添加--no-cache-dir避免缓存旧的错误包，同时确保先安装指定的setuptools和pip，再安装其他依赖：

# 假设基础镜像是Python2.7
FROM python:2.7-slim

WORKDIR /app

COPY requirements.txt .

# 先安装指定版本的setuptools和pip
RUN pip install --no-cache-dir setuptools==40.6.3 pip==1.5.4
# 再安装所有依赖
RUN pip install --no-cache-dir -r requirements.txt

# 其他构建步骤...

3. 验证依赖兼容性 #

如果仍有报错，可通过以下方式排查：

• 确认每个包的版本是否明确支持Python 2.7
• 使用pip install <package>==<version>单独测试安装，定位具体问题包
• 针对旧版pip，添加--use-deprecated=legacy-resolver参数优化依赖解析：

  pip install --use-deprecated=legacy-resolver --no-cache-dir -r requirements.txt
  

内容的提问来源于stack exchange，提问作者Akshay Jagtap