Doesnt seem to be a correct category to drop this, but the repo for packages has two broken packages on them.
ERROR: unable to update: download errors:
HTTP code 404 while fetching https://packages.confluent.io/deb/7.3/pool/main/c/confluent-libserdes/confluent-libserdes++1_7.3.9-1_amd64.deb
HTTP code 404 while fetching https://packages.confluent.io/deb/7.3/pool/main/libr/librdkafka/librdkafka++1_1.8.2~1confluent7.3.9-1_amd64.deb
When you check the url you get:
NoSuchKeyThe specified key does not exist.deb/7.3/pool/main/c/confluent-libserdes/confluent-libserdes 1_7.3.9-1_amd64.debZ38Z7W3ZHGJ4T9FYdij5t27YljxR8aWtvP4s4RoY0JWSVGG3/fQWHUEJlrU2HSj9DyHD82uaqTEB3PRfuyXIsIJKF+4=
And:
NoSuchKeyThe specified key does not exist.deb/7.3/pool/main/libr/librdkafka/librdkafka 1_1.8.2~1confluent7.3.9-1_amd64.debMYHG9KNXR626QWHYlpwkXzEP/oxzeF+ZjAf9D8NiNau8vVeIcdYN2YjraYvJMAALf34ldTcFt+u4/DrHBk4efuuCbCo=