Update the RHEL 8 / CentOS 8 install instructions
The `python3-markdown` package required by `tmt-test-convert` is
only available under extra repositories. Let's make it clear.
@@ -236,9 +236,12 @@ features right at hand install everything::
sudo dnf install tmt-all
For RHEL 8 and CentOS 8, first make sure that you have available
-the `EPEL <https://fedoraproject.org/wiki/EPEL>`_ repository::
+the `EPEL <https://fedoraproject.org/wiki/EPEL>`_ repository. You
+might also have to enable additional repositories::
sudo dnf install https://dl.fedoraproject.org/pub/epel/epel-release-latest-8.noarch.rpm
+ sudo dnf config-manager --enable powertools # CentOS 8
+ sudo dnf config-manager --enable rhel-CRB # RHEL 8
sudo dnf install tmt
For plugins which cannot work outside of VPN and so live within
