Expanding my comment to a complete answer.
salt-minion package is part of the Salt configuration management software. The Installation Documentation for Salt lists two ways of obtaining the packages required by Salt.
- Use the official SaltStack repository.
- Use the community-maintained EPEL repository.
The official repository contains the most up-to-date packages including the current version of Salt, 2018.3. The EPEL repository contains a much older version of the package, which is 2015.5.
As of version 2015.8, the EPEL repository is no longer required for installing Salt on RHEL systems.Therefore, the new packages may be installed purely from the offical repository. The official SaltStack repository for RHEL is located here.
The EPEL repository appears to have been abandoned sometime back due to a dependency problem - the installation document mentions that the packages
python-tornado-4.21 were not available in EPEL. These packages are now available as part of CentOS since 7.4.1708.
python-crypto-2.6.1 is available as part of the Extras repository, and
python-tornado-4.21 is available as part of the base repository.