OK I found --rpmverbosity=debug but I can't tell if it's helpful.
...snip...
Running scriptlet: kernel-core-4.14.0-1.fc28.x86_64
6/6
fdio: 2 writes, 104 total bytes in 0.000257 secs
D: --- h# 5501 kernel-core-4.14.0-1.fc28.x86_64
D: adding "kernel-core" to Name index.
D: adding 2325 entries to Basenames index.
D: adding "System Environment/Kernel" to Group index.
D: adding 13 entries to Requirename index.
D: adding 1742 entries to Providename index.
D: adding 2 entries to Conflictname index.
D: adding 383 entries to Dirnames index.
D: adding 1 entries to Installtid index.
D: adding 1 entries to Sigmd5 index.
D: adding "3f48bc22ee636457e7e7beb4338bee3a2125e3d0" to Sha1header index.
D: running post-transaction scripts
D: read h# 5504
Header SHA1 digest: OK
Header SHA256 digest: OK
D: Plugin: calling hook psm_pre in selinux plugin
D: %posttrans(kernel-core-4.14.0-1.fc28.x86_64): scriptlet start
D: %posttrans(kernel-core-4.14.0-1.fc28.x86_64): execv(/bin/sh) pid 2307
D: Plugin: calling hook scriptlet_fork_post in selinux plugin
D: setexecfilecon: (/bin/sh)
+ /bin/kernel-install add 4.14.0-1.fc28.x86_64
/lib/modules/4.14.0-1.fc28.x86_64/vmlinuz
cat: write error: Broken pipe
D: %posttrans(kernel-core-4.14.0-1.fc28.x86_64): waitpid(2307) rc 2307 status 0
Verifying : kernel-4.14.0-1.fc28.x86_64
1/6
Verifying : kernel-core-4.14.0-1.fc28.x86_64
2/6
Verifying : kernel-modules-4.14.0-1.fc28.x86_64
3/6
Verifying : kernel-4.14.0-1.fc28.x86_64
4/6
Verifying : kernel-modules-4.14.0-1.fc28.x86_64
5/6
Verifying : kernel-core-4.14.0-1.fc28.x86_64
6/6
Reinstalled: