The plugin cannot be deleted if any env exist

[Bulat Gaifullin]

It is not possible to delete plugin via fuel in case if any env exist in nailgun.
fuel shows error message that plugin already used by env, but actually there is no env where plugin is installed.

[Vitalii Myhal (xmig)]

Fixed in https://bugs.launchpad.net/fuel/+bug/1440046

Review: https://review.openstack.org/#/c/251194/

[Dmitriy Kruglov (dkruglov)]

Verified in MOS 8.0, build 367. The issue is fixed.

VERSION:
  feature_groups:
    - mirantis
  production: "docker"
  release: "8.0"
  api: "1.0"
  build_number: "367"
  build_id: "367"
  fuel-nailgun_sha: "20ff1666ea6171a085051ffd77444c52f972b7e7"
  python-fuelclient_sha: "4f234669cfe88a9406f4e438b1e1f74f1ef484a5"
  fuel-agent_sha: "1d2f6bc1123b9364ba65b41afcc0608662bb25b9"
  fuel-nailgun-agent_sha: "92ebd5ade6fab60897761bfa084aefc320bff246"
  astute_sha: "c7ca63a49216744e0bfdfff5cb527556aad2e2a5"
  fuel-library_sha: "6ec90013ed909997097563cddc762937dc873eb3"
  fuel-ostf_sha: "889ddb0f1a4fa5f839fd4ea0c0017a3c181aa0c1"
  fuel-mirror_sha: "8bb8c70efc61bcf633e02d6054dbf5ec8dcf6699"
  fuelmenu_sha: "824f6d3ebdc10daf2f7195c82a8ca66da5abee99"
  shotgun_sha: "63645dea384a37dde5c01d4f8905566978e5d906"
  network-checker_sha: "9f0ba4577915ce1e77f5dc9c639a5ef66ca45896"
  fuel-upgrade_sha: "616a7490ec7199f69759e97e42f9b97dfc87e85b"
  fuelmain_sha: "5dd650b541d40251e07afde4072d948be577dc0c"