pypandoc install fails of pandoc isn't installed

[haricot]

Collecting drf-schema-adapter
  Using cached drf-schema-adapter-0.9.52.tar.gz
    Complete output from command python setup.py egg_info:
    See http://johnmacfarlane.net/pandoc/installing.html
    for installation options
    ---------------------------------------------------------------
    
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-build-jy2sc7nj/drf-schema-adapter/setup.py", line 7, in <module>
        README = pypandoc.convert_file('README.md', 'rst')
      File "/home/path/venv/lib/python3.6/site-packages/pypandoc/__init__.py", line 140, in convert_file
        outputfile=outputfile, filters=filters)
      File "/home/path/venv/lib/python3.6/site-packages/pypandoc/__init__.py", line 260, in _convert_input
        _ensure_pandoc_path()
      File "/home/path/venv/lib/python3.6/site-packages/pypandoc/__init__.py", line 544, in _ensure_pandoc_path
        raise OSError("No pandoc was found: either install pandoc and add it\n"
    OSError: No pandoc was found: either install pandoc and add it
    to your PATH or or call pypandoc.download_pandoc(...) or
    install pypandoc wheels with included pandoc.
    
    ----------------------------------------