`VerificationError` should take an `Unknown` packet
@teythoon reports that:
I guess the proper fix is to have an
VerificationErrorthat can take an
VerificationError::MalformedSignaturetakes a signature. So we need a new variant.
Source: !1019 (comment 521134759)
This issue affects the bug reporting when verifying signatures: currently it's not possible to report that the verification failed due to an unknown packet (including broken MPIs).