ValueError: 'format' in __slots__ conflicts with class variable

[baldraider]

Unable to install with python 3 environment, getting this error while installing
`Collecting django-timelog
Cache entry deserialization failed, entry ignored
Using cached https://files.pythonhosted.org/packages/f8/81/08b354c2fb0eb132a855ad53a43a9ab740a40d63825bb98c3d8a094b8186/django-timelog-0.4.tar.gz
Collecting texttable (from django-timelog)
Cache entry deserialization failed, entry ignored
Using cached https://files.pythonhosted.org/packages/ba/16/ac997890d27d6a78e4bcb379ecd9ce105a0d923f4fefff2eb0c489697da0/texttable-1.2.1.tar.gz
Collecting progressbar (from django-timelog)
Cache entry deserialization failed, entry ignored
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 "", line 1, in
File "/private/var/folders/_9/2532sz1d6p1_916m2gccg4w00000gn/T/pip-install-q_lcmelj/progressbar/setup.py", line 5, in
import progressbar
File "/private/var/folders/_9/2532sz1d6p1_916m2gccg4w00000gn/T/pip-install-q_lcmelj/progressbar/progressbar/init.py", line 59, in
from progressbar.widgets import *
File "/private/var/folders/_9/2532sz1d6p1_916m2gccg4w00000gn/T/pip-install-q_lcmelj/progressbar/progressbar/widgets.py", line 121, in
class FileTransferSpeed(Widget):
File "/Users/sasuke/.virtualenvs/search-api/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

----------------------------------------

Command "python setup.py egg_info" failed with error code 1 in /private/var/folders/_9/2532sz1d6p1_916m2gccg4w00000gn/T/pip-install-q_lcmelj/progressbar/`