title: How to solve the error installing the python packages in virtualenv?
body: <p>I am installing some packages in my virtual environment by using pip, but it is showing me following error:</p>
  
  <p><code>pip install Flask-Ask==0.9.8</code></p>
  
  <p>and output is: </p>
  
  <p><code>Collecting Flask-Ask==0.9.8
    Using cached https://files.pythonhosted.org/packages/6a/f5/d4709ae94584a0b1541e9b52b2d25a8a1bdb6e2da9d6870f23fdd0523a30/Flask-Ask-0.9.8.tar.gz
      ERROR: Command errored out with exit status 1:
       command: /home/nisha/v2env/bin/python3.6 -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-wf2c65i_/Flask-Ask/setup.py'"'"'; __file__='"'"'/tmp/pip-install-wf2c65i_/Flask-Ask/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 /tmp/pip-install-wf2c65i_/Flask-Ask/pip-egg-info
           cwd: /tmp/pip-install-wf2c65i_/Flask-Ask/
      Complete output (5 lines):
      Traceback (most recent call last):
        File "&lt;string&gt;", line 1, in &lt;module&gt;
        File "/tmp/pip-install-wf2c65i_/Flask-Ask/setup.py", line 8, in &lt;module&gt;
          from pip.req import parse_requirements
      ModuleNotFoundError: No module named 'pip.req'
      ----------------------------------------
  ERROR: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.
  </code></p>