Throw error from getAuthAccount when account doesn't exist

[ishantiw]

Description

The getAuthAccount method implementation differs from LIP-0041. The LIP says the implementation should raise an exception when no account exists. The implementation returns a default account when no account exists.

Which version(s) does this affect? (Environment, OS, etc...)

v6.0.0-beta.6

[bobanm]

As agreed with @shuse2, in this case it makes more sense to keep the implementation as it is, and align the LIP. That would align behavior of getAuthAccount() with behavior of getAvailableBalance() and getEscrowedAmount(), where LIP-0051 specifies that for a non-existing key the system should return 0 as the default value.

I opened the issue in LIP repo.