## Issue Addressed
NA
## Proposed Changes
Whilst investigating #2372, I [learned](https://github.com/sigp/lighthouse/issues/2372#issuecomment-851725049) that the error message returned from some failed Eth1 requests are always `NotReachable`. This makes debugging quite painful.
This PR adds more detail to these errors. For example:
- Bad infura key: `ERRO Failed to update eth1 cache error: Failed to update Eth1 service: "All fallback errored: https://mainnet.infura.io/ => EndpointError(RequestFailed(\"Response HTTP status was not 200 OK: 401 Unauthorized.\"))", retry_millis: 60000, service: eth1_rpc`
- Unreachable server: `ERRO Failed to update eth1 cache error: Failed to update Eth1 service: "All fallback errored: http://127.0.0.1:8545/ => EndpointError(RequestFailed(\"Request failed: reqwest::Error { kind: Request, url: Url { scheme: \\\"http\\\", cannot_be_a_base: false, username: \\\"\\\", password: None, host: Some(Ipv4(127.0.0.1)), port: Some(8545), path: \\\"/\\\", query: None, fragment: None }, source: hyper::Error(Connect, ConnectError(\\\"tcp connect error\\\", Os { code: 111, kind: ConnectionRefused, message: \\\"Connection refused\\\" })) }\"))", retry_millis: 60000, service: eth1_rpc`
- Bad server: `ERRO Failed to update eth1 cache error: Failed to update Eth1 service: "All fallback errored: http://127.0.0.1:8545/ => EndpointError(RequestFailed(\"Response HTTP status was not 200 OK: 501 Not Implemented.\"))", retry_millis: 60000, service: eth1_rpc`
## Additional Info
NA
ba9c4c5eea