Installing python3 progressbar on Mac

I was about to install progressbar on my Mac but unfortunately I failed with the message below:

pip install progressbar

Collecting progressbar

  Using cached https://files.pythonhosted.org/packages/0f/e1/f30b72ecabba259c7c38dd0eb944a173effced3fd7de2c9c2902bd6f649a/progressbar-2.3.tar.gz

    Complete output from command python setup.py egg_info:

    Traceback (most recent call last):

      File "<string>", line 1, in <module>

      File "/private/var/folders/v3/jgccrlps71lc9_9j_gx74mzm0000gp/T/pip-install-sgrrpp2s/progressbar/setup.py", line 5, in <module>

        import progressbar

      File "/private/var/folders/v3/jgccrlps71lc9_9j_gx74mzm0000gp/T/pip-install-sgrrpp2s/progressbar/progressbar/__init__.py", line 59, in <module>

        from progressbar.widgets import *

      File "/private/var/folders/v3/jgccrlps71lc9_9j_gx74mzm0000gp/T/pip-install-sgrrpp2s/progressbar/progressbar/widgets.py", line 121, in <module>

        class FileTransferSpeed(Widget):

      File "/Users/alfred/.virtualenvs/dl4cv/bin/../lib/python3.6/abc.py", line 133, in __new__

        cls = super().__new__(mcls, name, bases, namespace, **kwargs)

    ValueError: 'format' in __slots__ conflicts with class variable

To resolve that, use the command below instead:

pip3 install progressbar33