>>109589736
Here's your problem,
debug: database path for tree core set to /var/lib/pacman/sync/core.db
debug: "/var/lib/pacman/sync/core.db.sig" is not readable: No such file or directory
debug: sig path /var/lib/pacman/sync/core.db.sig could not be opened
debug: got error 43 at _alpm_gpgme_checksig (../lib/libalpm/signing.c: 565) : missing PGP signature
For whatever reason, your core repo db has no signature file, or its permissions are fucked.
Check ls -l /var/lib/pacman/sync
I'm not sure what the fix is for this just yet.