Errors for: pip install gunicorn

pip install gunicorn
Downloading/unpacking gunicorn
  Downloading gunicorn-19.7.1-py2.py3-none-any.whl (111kB): 111kB downloaded
Installing collected packages: gunicorn
Compiling /tmp/pip_build_root/gunicorn/gunicorn/workers/_gaiohttp.py ...
  File "/tmp/pip_build_root/gunicorn/gunicorn/workers/_gaiohttp.py", line 84
    yield from self.wsgi.close()
             ^
SyntaxError: invalid syntax

Successfully installed gunicorn
Cleaning up...