This might happen if for some reason the link /etc/profile.d/modules.sh
is missing or some other problem with alternatives.

/etc/profile.d/scl-init.sh has:

if [ "${MODULEPATH:-}" = "" ]; then
   MODULEPATH=`sed -n 's/[   #].*$//; /./H; $ { x; s/^\n//; s/\n/:/g; p; }' ${MODULESHOME}/init/.modulespath`
fi

but there is no /usr/share/Modules/.modulespath file, that should be now
legacy.

Maybe /etc/profile.d/scl-init.sh should check if that file exist before the
sed command, or, maybe better print a warning telling MODULEPATH is not
defined.

In either case, this is a way to detect problems with alternatives and
missing environment-modules initialization.

This should be a minimal issue, just that some message should still be
printed, but better if not a sed error message about a missing file, like:

sed: can't read /usr/share/Modules/init/.modulespath: No such file or directory

for every shell login.