报错信息
使用 pip 安装依赖时的报错如下：
Collecting markupsafe==1.0
Downloading https://.../MarkupSafe-1.0.tar.gz (14 kB)
ERROR: Command errored out with exit status 1:
command: '...\python.exe' -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'...\\pip-install-bsormril\\markupsafe\\setup.py'"'"'; __file__='"'"'...\\pip-install-bsormril\\markupsafe\\setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base '...\pip-install-bsormril\markupsafe\pip-egg-info'
cwd: ...\pip-install-bsormril\markupsafe\
Complete output (5 lines):
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "...\pip-install-bsormril\markupsafe\setup.py", line 6, in <module>
from setuptools import setup, Extension, Feature
ImportError: cannot import name 'Feature'
----------------------------------------
ERROR: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.使用 Pipenv 安装依赖时的报错如下：
An error occurred while installing markupsafe==1.0 --hash=sha256:a6be69091dac236ea9c6bc7d012beab42010fa914c459791d627dad4910eb665! Will try again.
Installing initially failed dependencies…
[pipenv.exceptions.InstallError]: File "...\Python\Python36\site-packages\pipenv\core.py", line 1874, in do_install
[pipenv.exceptions.InstallError]: keep_outdated=keep_outdated
[pipenv.exceptions.InstallError]: File "...Python\Python36\site-packages\pipenv\core.py", line 1253, in do_init
[pipenv.exceptions.InstallError]: pypi_mirror=pypi_mirror,
[pipenv.exceptions.InstallError]: File "...\Python\Python36\site-packages\pipenv\core.py", line 859, in do_install_dependencies
[pipenv.exceptions.InstallError]: retry_list, procs, failed_deps_queue, requirements_dir, **install_kwargs
[pipenv.exceptions.InstallError]: File "...\Python\Python36\site-packages\pipenv\core.py", line 763, in batch_install
[pipenv.exceptions.InstallError]: _cleanup_procs(procs, not blocking, failed_deps_queue, retry=retry)
[pipenv.exceptions.InstallError]: File "...\Python\Python36\site-packages\pipenv\core.py", line 681, in _cleanup_procs
[pipenv.exceptions.InstallError]: raise exceptions.InstallError(c.dep.name, extra=err_lines)
[pipenv.exceptions.InstallError]: ['Looking in indexes: https://.../pypi/simple', 'Collecting markupsafe==1.0', ' Using cached https://.../MarkupSafe-1.0.tar.gz (14 kB)']
[pipenv.exceptions.InstallError]: ['ERROR: Command errored out with exit status 1:', '
command: \'...\\.virtualenvs\\helloflask-evdb6idn\\scripts\\python.exe\' -c \'import sys, setuptools, tokenize; sys.argv[0] = \'"\'"\'...\pip-install-pkgojp4t\\\\markupsafe\\\\setup.py\'"\'"\';
__file__=\'"\'"\'...\\\\pip-install-pkgojp4t\\\\markupsafe\\\\setup.py\'"\'"\';f=getattr(tokenize, \'"\'"\'open\'"\'"\', open)(__file__);code=f.read().replace(\'"\'"\'\\r\\n\'"\'"\', \'"\'"\'\\n\'"\'"\');f.close();exec(compile(code, __file__, \'"\'"\'exec\'"\'"\'))\' egg_info --egg-base \'...\\pip-install-pkgojp4t\\markupsafe\\pip-egg-info\'', '
cwd: ...\\pip-install-pkgojp4t\\markupsafe\\', ' Complete output (5 lines):', '
Traceback (most recent call last):', '
File "<string>", line 1, in <module>', '
File "...\\pip-install-pkgojp4t\\markupsafe\\setup.py", line 6, in <module>', '
from setuptools import setup, Extension, Feature', "
ImportError: cannot import name 'Feature'", '----------------------------------------',
'ERROR: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.']
ERROR: ERROR: Package installation failed...其他工具输出类似，主要异常信息是 MarkupSafe setup.py: ImportError: cannot import name Feature。通常会在安装 Flask 项目的依赖时发生，因为 MarkupSafe 是 Flask 的依赖之一。
原因和解决方法
出现这个报错的原因是因为 Python 打包工具 setuptools 在 46.0.0 版本删掉了弃用的 Feature，而 MarkupSafe 刚好在 setup.py 文件里导入了这个类，所以会出现报错。
解决方法很多，最直接的是更新 MarkupSafe 到最新版本（1.1.1），新版本去掉了对 Feature 类的导入。如果使用 requirements.txt 存储依赖列表，那就把 MarkupSafe 的版本号改成 1.1.1（找到 MarkupSafe 开头那一行，替换版本号）：
MarkupSafe==1.1.1然后重新执行：
$ pip install -r requirements.txt