access to vault to have better error message

[dzmitry-lahoda]

try next with wrong az account:

    let mut key_vault_client = KeyVaultClient::new(&creds, "lahodapro");
    println!("list secrets for");
    let secrets = key_vault_client.list_secrets().await?;

Expected: error message about wrong auth usage
Actual: error about some value is missing
Notes: that is very important that entry point to azure via auth to have guiding errors, not cryptic

[guywaldman]

Thanks, agree. I kept it very simple and a lot of the errors can be improved now that it's part of the official repo.

Speaking of, noticed that the error message here is not accurate, should accommodate endpoints in other clouds.

[ftt]

I think this should be covered by [Proposal] Error Handling #625.

[rylev]

Just as an FYI: #625 won't solve this but it does provide facilities for improving the error message.