Fedora 27 updating fails.
I ran dnf clean packages with no results.

elta RPMs reduced 129.2 MB of updates to 129.0 MB (0.1% saved)
warning: /var/cache/dnf/livna-cec64278843bd06c/packages/libdvdcss-1.4.1-1.fc27.remi.x86_64.rpm: Header V4 RSA/SHA256 Signature, key ID 0364b949: NOKEY
Importing GPG key 0xA109B1EC:
Userid : "Livna.org rpms <rpm-key@livna.org>"
Fingerprint: 037B 5D9B E1B6 B673 2A23 13B5 7129 5441 A109 B1EC
From : /etc/pki/rpm-gpg/RPM-GPG-KEY-livna
Key imported successfully
Import of key(s) didn't help, wrong key(s)?
Public key for libdvdcss-1.4.1-1.fc27.remi.x86_64.rpm is not installed. Failing package is: libdvdcss-1.4.1-1.fc27.remi.x86_64
GPG Keys are configured as: file:///etc/pki/rpm-gpg/RPM-GPG-KEY-livna
The downloaded packages were saved in cache until the next successful transaction.
You can remove cached packages by executing 'dnf clean packages'.
Error: GPG check FAILED

What is the exact command you're running to generate this? I can see you answered "Y" to import the new keys, but not what you're trying to do. Try:
...to sidestep the GPG check (**NOT** too secure, check your sources first)

# dnf -y --nogpgcheck
usage: dnf [options] COMMAND

It spits out all the dnf commands, like it doesn't like the command.
--nogpgcheck is a legal command, what gives here ?

Obviously a syntax error of some sort. Aside from the man page, there isn't much I can tell you...did you try leaving off the -y?

This is the command I should have used.
# dnf -y update --nogpgcheck

Thanks for your help.