title: Invalid requirement, parse error at "'--instal'" while trying to use --install-option in requirements.txt
body: <p>I'm trying to install a python module using setup.py with requirements.txt. I'm installing the module using <code>pip install -U .</code> in the directory where I have a <code>setup.py</code> file. </p>
  
  <p>My <code>setup.py</code> file parses the <code>requirements.txt</code> file by storing the requirements in a list of strings:</p>
  
  <pre><code>def get_requirements():
      root_path = os.path.abspath(os.path.dirname(__file__))
      requirements_file_path = os.path.join(root_path, 'requirements.txt')
  
      # example: `numpy &gt;= 1.13`
      with open(requirements_file_path) as file:
          requirements = [requirement.strip() for requirement in file.readlines()]
          requirements = filter(lambda requirement: len(requirement), requirements)
          requirements = filter(lambda requirement: not requirement.startswith('-'), requirements)
          requirements = list(requirements)
  
      return requirements
  
  requirements = get_requirements()
  config = {'name': name, 
            'install_requires': requirements
  }
  setuptools.setup(**config)
  </code></pre>
  
  <p>My requirements file looks like:</p>
  
  <pre><code>numpy &gt;= 1.13
  pyyaml &gt;= 3.12
  matplotlib
  opencv-python &gt;= 3.2
  setuptools
  cython
  mock
  scipy
  six
  future
  protobuf
  yacs
  ninja
  colour
  torchvision_nightly
  torch_nightly --install-option="--find-links https://download.pytorch.org/whl/nightly/cu92/torch_nightly.html"
  </code></pre>
  
  <p>However, when I try to install the module with <code>pip install -U .</code>, I get the following parsing error:</p>
  
  <pre><code>Processing /home/my-module
      Complete output from command python setup.py egg_info:
      error in my_module setup command: 'install_requires' must be a string or list of strings containing valid project/version requirement specifiers; Invalid requirement, parse error at "'--instal'"
  
  ----------------------------------------
  </code></pre>
  
  <p>Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-req-build-rf9439sf/</p>
  
  <p>Any idea on why passing <code>--install-option</code> causes a parse error?</p>