postgres wal sender replication timeout during pg_basebackup
Many thanks to Albe Laurenz from the pgsql-admin mailing list.

The server error message means that the client did not send a status update within wal_sender_timeout milliseconds, see documentation.

The basebackup needs to complete before this wal_sender_timeout period, else the server resets the connection.

Side note, I am running 9.2 so this parameter is called replication_timeout in the older version.