The package naming for pip has changed in centos8. Previously the pip
package was called python-pip for python2 and python3-pip for python3.
In CentOS 8 the packages are now called python2-pip for python2 ad
python3-pip for python3.
On Amazon Linux, installing `python-pip` acutally installs the
`python26-pip` package, so anything running in Python 2.7 won't
find the dependencies installed with that `pip`.
This allows the package name to be customised, depending on the OS
and Python versions.
