UI and python client get the error types and error docs from metadata about subtensor HOT 6 OPEN

Synced with the @opentensor/cortex peeps, this is how we will pass it to them:

We will add an RPC call that produces a JSON map of all error codes => { name, description } for each error. Client will hold off on calling this RPC endpoint until the first time they encounter an error, then they will hit the endpoint and cache the map (probably in a local file). Later, if they ever hit an error code that isn't in their local map, they will hit the endpoint again. In this way, we will always be able to display names and descriptions for errors coming from subtensor, even if new ones are introduced in a chain upgrade that bittensor doesn't specifically know about.

cc @unconst ^

so data coming back from that endpoint will look something like:

{
    "0": {
        "name": "SomeError",
        "description": "Thrown when yeet and something something"
    },
    "1": {
        "name": "AnotherError",
        "description": "This is a description something something"
    },
    "2": {
        "name": "YetAnotherError",
        "description": "This is a description something something"
    }
}

from subtensor.

I would recommend doing something like this rather than Display actually:

pub trait SubtensorError {
    const NAME: &'static str;
    const DESCRIPTION: &'static str;
}

from subtensor.

Related : #375 cc @camfairchild

from subtensor.

partially fixed by #391

from subtensor.

right now it looks like the way forward is actually just using regular substrate metadata, which @open-junius has implemented in #391

from subtensor.

From this unit test file for metadata, the structure is clear for other language like python to parse.
https://github.com/opentensor/subtensor/blob/development/runtime/tests/metadata.rs

from subtensor.