### Bug Description When the snap is built with the following section: ```yaml assumes: - command-chain ``` The snap cannot be uploaded to snap store with the following error: ``` $ review-tools.snap-review -v tempest_39.0.0_amd64.snap Errors ------ - lint-snap-v2:snap_schema Error found while validating snap.json::$.assumes: ['command-chain', 'command-chain'] has non-unique elements ``` ### To Reproduce The bug can be reproduce using the tempest snap as an example: https://github.com/canonical/snap-tempest/blob/main/snap/snapcraft.yaml I believe other snap with ```yaml assumes: - command-chain ``` will also fail to upload ### Environment using `snapcraft 8.3.1 12136 latest/stable/… canonical✓ classic` ### snapcraft.yaml ```shell See "To Reproduce" section ``` ### Relevant log output ```shell Errors ------ - lint-snap-v2:snap_schema Error found while validating snap.json::$.assumes: ['command-chain', 'command-chain'] has non-unique elements ``` ### Additional context An inspection of `/snap/tempest/current/meta/snap.yaml` showed that somehow `assumes` contains a duplicated `command-chain` ``` cat /snap/tempest/current/meta/snap.yaml ``` ```yaml name: tempest version: 39.0.0 summary: OpenStack Integration Test Suite description: | Tempest is a set of integration tests to be run against a live OpenStack cluster. Tempest has batteries of tests for OpenStack API validation, Scenarios, and other specific tests useful in validating an OpenStack deployment. license: Apache-2.0 architectures: - amd64 base: core22 assumes: - command-chain - command-chain apps: tempest: command: bin/tempest completer: usr/share/bash-completion/completions/tempest plugs: - network-observe - network - home environment: TESTS: $SNAP_DATA/tempest_test_lists command-chain: - bin/tempest-wrapper discover: command: bin/discover-tempest-config plugs: - home - network environment: SSL_CERT_FILE: $OS_CACERT confinement: strict grade: stable environment: LD_LIBRARY_PATH: ${SNAP_LIBRARY_PATH}${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}:$SNAP/lib PATH: $SNAP/usr/sbin:$SNAP/usr/bin:$SNAP/sbin:$SNAP/bin:$PATH ```