Improve error handling during replication download #257
Description
The replication handler currently catches all errors that happen during download of diff files and ends the download process as if it was finished. The idea behind this is that a continuous script will simply want to retry on transient errors. However there are some permanent errors that really should be reported back as such. A 404 on a state or diff file would be such a condition.
See also osm2pgsql-dev/osm2pgsql#2206.