loading plpython error

We have installed from the YUM repo.  The server runs fine but we are trying to add python support.

yum install postrgesql11-contrib postgresql11-plpython

I can see the installed files in the correct locations but when we invoke create extension, we are greeted with the following error:

Is there something yet to be installed?  Is this a package error?  Any hints to fixing?

thanks

alan