yum update command returns "Bad magic number in /usr/bin/_weakref.pyc" ?

Issue

• On yum update, yum command returns Bad magic number in /usr/bin/_weakref.pyc.

# yum update
There was a problem importing one of the Python modules
required to run yum. The error leading to this problem was:

   Bad magic number in /usr/bin/_weakref.pyc

Please install a package which provides this module, or
verify that the module is installed correctly.