When a build is triggered, it could be marked as to be skipped by builders if:

* there is already a build running/queued for the same commit

  Multiple builds of the same commit will lead to the same results. So, we skip
  it if there is one already running/queued.

* there is already a build queued for the same version

  When building a version without specifying the commit, the last commit is
  built. In this case, we can only skip the new triggered build if there is one
  build queued because both builds will just pick the same commit.

…humitos/de-duplicate-builds

Django does not convert Enum automatically to its value :/