1. The error information is as follows:

$ sudo pip install bs4==0.0.1
Collecting bs4==0.0.1
  Downloading http://pip.pgw.getui.com/packages/10/ed/7e8b97591f6f456174139ec089c769f89a94a1a4025fe967691de971f314/bs4-0.0.1.tar.gz
Collecting beautifulsoup4 (from bs4==0.0.1)
  Downloading http://pip.pgw.getui.com/packages/a1/69/daeee6d8f22c997e522cdbeb59641c4d31ab120aba0f2c799500f7456b7e/beautifulsoup4-4.10.0.tar.gz (399kB)
    100% |████████████████████████████████| 409kB 11.7MB/s
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-build-USqeae/beautifulsoup4/setup.py", line 7, in <module>
        from bs4 import __version__
      File "bs4/__init__.py", line 36, in <module>
        raise ImportError('You are trying to use a Python 3-specific version of Beautiful Soup under Python 2. This will not work. The final version of Beautiful Soup to support Python 2 was 4.9.3.')
    ImportError: You are trying to use a Python 3-specific version of Beautiful Soup under Python 2. This will not work. The final version of Beautiful Soup to support Python 2 was 4.9.3.

    ----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-build-USqeae/beautifulsoup4/

2 solution

Install beatifulsoup4 first

$ sudo  pip install beautifulsoup4==4.9.0
Collecting beautifulsoup4==4.9.0
  Downloading http://pip.pgw.getui.com/packages/2d/3e/8b2fc5d3c31c84d7209313f4059858f502f2e4a9d986693eca03fe325565/beautifulsoup4-4.9.0-py2-none-any.whl (109kB)
    100% |████████████████████████████████| 112kB 872kB/s
Collecting soupsieve<2.0 (from beautifulsoup4==4.9.0)
  Downloading http://pip.pgw.getui.com/packages/39/36/f35056eb9978a622bbcedc554993d10777e3c6ff1ca24cde53f4be9c5fc4/soupsieve-1.9.6-py2.py3-none-any.whl
Collecting backports.functools-lru-cache; python_version < "3" (from soupsieve<2.0->beautifulsoup4==4.9.0)
  Downloading http://pip.pgw.getui.com/packages/e5/c1/1a48a4bb9b515480d6c666977eeca9243be9fa9e6fb5a34be0ad9627f737/backports.functools_lru_cache-1.6.4-py2.py3-none-any.whl
Installing collected packages: backports.functools-lru-cache, soupsieve, beautifulsoup4
Successfully installed backports.functools-lru-cache-1.6.4 beautifulsoup4-4.9.0 soupsieve-1.9.6

Installing BS4

$ sudo  pip install  bs4==0.0.1
Collecting bs4==0.0.1
  Downloading http://pip.pgw.getui.com/packages/10/ed/7e8b97591f6f456174139ec089c769f89a94a1a4025fe967691de971f314/bs4-0.0.1.tar.gz
Requirement already satisfied (use --upgrade to upgrade): beautifulsoup4 in /usr/lib/python2.7/site-packages (from bs4==0.0.1)
Requirement already satisfied (use --upgrade to upgrade): soupsieve<2.0 in /usr/lib/python2.7/site-packages (from beautifulsoup4->bs4==0.0.1)
Requirement already satisfied (use --upgrade to upgrade): backports.functools-lru-cache; python_version < "3" in /usr/lib/python2.7/site-packages (from soupsieve<2.0->beautifulsoup4->bs4==0.0.1)
Installing collected packages: bs4
  Running setup.py install for bs4 ... done
Successfully installed bs4-0.0.1