virtualenv创建Python虚拟环境时抛出UnicodeDecodeError异常的解决

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  在通过pip安装TensorFlow时遇到了一个问题，当执行virtualenv --system-site-packages -p python ./venv创建新的虚拟环境时会抛出如下异常：

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Traceback (most recent call last):
  File "e:\python\lib\site-packages\virtualenv.py", line 939, in call_subprocess
    line = line.decode(encoding)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xca in position 38: invalid continuation byte

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "e:\python\lib\site-packages\virtualenv.py", line 2635, in <module>
    main()
  File "e:\python\lib\site-packages\virtualenv.py", line 870, in main
    symlink=options.symlink,
  File "e:\python\lib\site-packages\virtualenv.py", line 1173, in create_environment
    install_wheel(to_install, py_executable, search_dirs, download=download)
  File "e:\python\lib\site-packages\virtualenv.py", line 1019, in install_wheel
    _install_wheel_with_search_dir(download, project_names, py_executable, search_dirs)
  File "e:\python\lib\site-packages\virtualenv.py", line 1110, in _install_wheel_with_search_dir
    call_subprocess(cmd, show_stdout=False, extra_env=env, stdin=script)
  File "e:\python\lib\site-packages\virtualenv.py", line 941, in call_subprocess
    line = line.decode(fs_encoding)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xca in position 38: invalid continuation byte

  经过一番研究，原来出现异常的原因是调用decode()方法的errors参数为默认值"strict"，即任何编码错误都会引发UnicodeDecodeError，将其更改为"ignore"即可忽略错误。具体修改如下：
  根据异常信息，将Python安装目录下的.\Lib\site-packages\virtualenv.py的第939行修改为line = line.decode(encoding, "ignore")，即增加一个"ignore"参数。
再次尝试创建虚拟环境，此时就不会抛出异常了：

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Running virtualenv with interpreter E:\Python\python.exe
Already using interpreter E:\Python\python.exe
Using base prefix 'E:\\Python'
New python executable in D:\TensorFlow\venv\Scripts\python.exe
Installing setuptools, pip, wheel...
done.

  这时我们就拥有了一套独立的Python运行环境，不用担心污染主环境了