AttributeError: 'HTTPClient' object has no attribute '_closed'

Gaffer version: **gaffer version 0.5.2**

I have a `Django 2.0` application deployed on `VPS` with virtual environment setup using `pipenv`.

At present, using this command to run the application from terminal in background.

/root/.local/bin/pipenv run /home/user/.local/share/virtualenvs/app.application.com-IuTkL8w_/bin/gunicorn myapp.wsgi:application &

Now, I want to configure using `Procfile` and `gaffer`.

I added a file `Procfile` to root of the application directory with command

web: gunicorn myapp.wsgi --log-file - --log-level debug

and trying to load it with `gaffer`

$ cd myproject
$ gaffer load Procfile

but it is giving error as

Traceback (most recent call last):
File "/usr/local/bin/gaffer", line 11, in
sys.exit(main())
File "/usr/local/lib/python3.6/site-packages/gaffer/cli/main.py", line 252, in main
cli.run()
File "/usr/local/lib/python3.6/site-packages/gaffer/cli/main.py", line 193, in run
config = Config(self.args)
File "/usr/local/lib/python3.6/site-packages/gaffer/cli/main.py", line 87, in __init__
api_key=api_key, **self.client_options)
File "/usr/local/lib/python3.6/site-packages/gaffer/httpclient/server.py", line 22, in __init__
super(Server, self).__init__(uri, loop=loop, **options)
File "/usr/local/lib/python3.6/site-packages/gaffer/httpclient/base.py", line 86, in __init__
self.client = HTTPClient(loop=loop)
File "/usr/local/lib/python3.6/site-packages/gaffer/httpclient/base.py", line 42, in __init__
self._io_loop = IOLoop(_loop=loop)
File "/usr/local/lib/python3.6/site-packages/gaffer/tornado_pyuv.py", line 54, in __init__
self._waker = Waker(self._loop)
File "/usr/local/lib/python3.6/site-packages/gaffer/tornado_pyuv.py", line 28, in __init__
self._async.unref()
AttributeError: 'pyuv._cpyuv.Async' object has no attribute 'unref'
Exception ignored in: >
Traceback (most recent call last):
File "/usr/local/lib/python3.6/site-packages/gaffer/httpclient/base.py", line 50, in __del__
self.close()
File "/usr/local/lib/python3.6/site-packages/gaffer/httpclient/base.py", line 54, in close
if not self._closed:
AttributeError: 'HTTPClient' object has no attribute '_closed'

**How to solve this `AttributeError: 'HTTPClient' object has no attribute '_closed'` error?**