Unable to upgrade from RHEL6 to RHEL7

Getting this error when running "preupg --riskcheck --verbose" command before upgrading.

preupg.risk.EXTREME: You have the GNOME desktop environment session as an option in your X11 session manager. The GNOME desktop environment as a part of the 'Desktop' yum group underwent a serious redesign in its user interface as well as in underlying technologies in Red Hat Enterprise Linux 7.
preupg.risk.EXTREME: You have the KDE desktop environment session as an option in your X11 session manager. The KDE desktop environment as a part of the yum group 'KDE Desktop' underwent a redesign in its user interface as well as in underlying technologies in Red Hat Enterprise Linux 7.

I've tried removing both KDE and Gnome through yum. Even after removing them the preupg check still gives me the same error message. So I tried rebooting and then the system just froze when it tried to restart. Guessing something is trying to launch the desktop environment and there is no longer anything there to run. It just freezes solid and I'm unable to even ping or ssh to the server.

Any advice appreciated.