update-keys: switch to keyserver keyserver.ubuntu.com

As the SKS infrastructure is offline for good, we need to switch to
keyserver.ubuntu.com for the time being.

The Ubuntu keyservers to not support EC keys, thus we have to ignore
failure when refreshing keys.

update-keys

@@ -9,7 +9,7 @@ export LANG=C
 TMPDIR=$(mktemp -d)
 trap "rm -rf '${TMPDIR}'" EXIT
 
-KEYSERVER='hkp://pool.sks-keyservers.net'
+KEYSERVER='hkps://keyserver.ubuntu.com'
 GPG=(gpg --homedir "${TMPDIR}")
 
 cat << __EOF__ > "${TMPDIR}"/gpg.conf
@@ -49,7 +49,9 @@ while read -ra data; do
 	keyid="${data[0]}"
 	username="${data[@]:1}"
 	if "${GPG[@]}" --list-keys ${keyid} >/dev/null &>/dev/null; then
-		"${GPG[@]}" --refresh-keys ${keyid} &>/dev/null
+		# Ignore refresh failure; Ubuntu keyserver lacks support for EC keys
+		# TODO: Remove the "|| true" when the above is no longer an issue
+		"${GPG[@]}" --refresh-keys ${keyid} &>/dev/null || true
 	else
 		"${GPG[@]}" --recv-keys ${keyid} &>/dev/null
 	fi