togran

Harvester raises an error while processing blocks on Polkadot CC1

9

Occasionally harvester_worker raises an error and refuses to process blocks anymore ```harvester-worker_1 | [2020-06-04 14:14:10,021: ERROR/ForkPoolWorker-1] Task app.tasks.start_sequencer[49e40ce4-6ad3-4d20-90ce-609464c66230] raised unexpected: ValueError("Index '202' not present in Enum value list",) harvester-worker_1 |...

This is a secondary PR to main PR in polkadot-os [link](https://github.com/polkascan/polkascan-os/pull/19)