Why does subscription manager command fail with error: pkg_resources.DistributionNotFound: ethtool

Issue

• Subscription manager failed with the following error.

  # subscription-manager status
  Traceback (most recent call last):
   File "/sbin/subscription-manager", line 5, in <module>
     from pkg_resources import load_entry_point
   File "/usr/lib/python2.7/site-packages/pkg_resources.py", line 3007, in <module>
     working_set.require(__requires__)
   File "/usr/lib/python2.7/site-packages/pkg_resources.py", line 728, in require
     needed = self.resolve(parse_requirements(requirements))
   File "/usr/lib/python2.7/site-packages/pkg_resources.py", line 626, in resolve
     raise DistributionNotFound(req)
  pkg_resources.DistributionNotFound: ethtool