USN notification service is failing to detect affected binary packages if dpkg.list file is present and binary contains arch specifier

[Emilia Torino]

Some special snaps could ship a dpkg.list file (e.g. core snaps). If that's the case, review-tools adds each of the binaries present in such file, as stage-packages in a "faked-by-review-tools-dpkg" fake part. Those binaries are then inspected against the USN db to detect security updates affecting them.

Under certain circumstances, the binary name in the dpkg.list entry could contain an architecture specifier as part of the binary name (e.g liblz4-1:amd64). The review-tools is not considering such situation and is setting the binary name as liblz4-1:amd64 when it should be liblz4-1 only.

This issue makes the the USN notification service to fail detect USNs affecting such binary packages as it uses binary names to compare.

$ review-tools.check-notices core18_2066.snap
{
  "core18": {
    "2066": {}
  }
}

With 2021/05/27 USN DB it should report:
{
  "isc-dhcp-client": [
    "4969-1"
  ],
  "liblz4-1": [
    "4968-1"
  ]
}

There is a related bug which is related to the presence of an empty primed-stage-packages: [] in the snap manifest which also affects this result: https://bugs.launchpad.net/review-tools/+bug/1930106. Both bugs need to be resolved together for this result to be properly provided.