These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.52 s (backtrack: 0/20).

[ebuild  N     ] sys-apps/seedfiles-1.6::gentoo  58 KiB
[blocks B      ] sys-apps/systemd-utils[tmpfiles] ("sys-apps/systemd-utils[tmpfiles]" is soft blocking sys-apps/seedfiles-1.6)

Total: 1 package (1 new), Size of downloads: 58 KiB
Conflict: 1 block (1 unsatisfied)

 * Error: The above package list contains packages which cannot be
 * installed at the same time on the same system.

  (sys-apps/systemd-utils-259.4:0/0::gentoo, installed) pulled in by
    sys-apps/systemd-utils[udev] required by (virtual/udev-217-r7:0/0::gentoo, installed) USE="(-systemd)"
    sys-apps/systemd-utils[tmpfiles] required by (virtual/tmpfiles-0-r5:0/0::gentoo, installed) USE="(-systemd)"

  (sys-apps/seedfiles-1.6:0/0::gentoo, ebuild scheduled for merge) pulled in by
    =sys-apps/seedfiles-1.6


For more information about Blocked Packages, please refer to the following
section of the Gentoo Linux x86 Handbook (architecture is irrelevant):

https://wiki.gentoo.org/wiki/Handbook:X86/Working/Portage#Blocked_packages