Previously Tuned RPM patched unconditionally grub configuration files to support alteration of kernel command line through tuned profiles (by using bootloader plugin). But there are architectures like s390(x) where grub isn't supported.
On such architectures Tuned installation/upgrade ended with error message.
Conditional support for grub was added into Tuned RPM.
Now the Tuned RPM scriptlet patches grub configuration files only if grub is installed on the machine and the error is no more triggered on s390(x).