Eliminate the BlobsNotFound error from the test test_end_to_end_assign_greatgrandchild_chain

[MathieuDutSik]

Motivation

The test test_end_to_end_assign_greatgrandchild_chain returns a BlobsNotFound error.
This error arises from the

    let wrong_id = ChainId(CryptoHash::test_hash("wrong chain ID"));
    let result = client3.follow_chain(wrong_id, false).await;
    assert!(result.is_err());

The problem is that the FollowChain is a functionality that any user could use. On the other hand, the BlobsNotFound is an internal error of the protocol and client code:

• This is confusing for users: Instead of having a clear error of a non-existing chain, the user gets an internal error message.
• This is confusing for developers: It leaves the impression that there are still some protocol errors.

The BlobsNotFound error is present in NodeError and LocalNodeError. This is one degree of uncertainty in the error.

Proposal

Catch the specific BlobsNotFound error and reformulate the error.
This makes the system work.

Test Plan

The test remains the same. There is still an ERROR statement, but the one that shows up is now quite clear.

Release Plan

This is of interest to the TestNet Conway.
It means that if a BlobsNotFound error occurs in the test, then we know that they are not related to wrong input.

Links

None.

[afck]

I'm not sure about this: It makes follow-chain report the same error differently than other commands.

[MathieuDutSik]

I'm not sure about this: It makes follow-chain report the same error differently than other commands.

I agree.
We discussed that. What we want is better error processing. Will work on that.