message: `conflicting_activations` should always apply to `cx`
  This is a small assert, but it scuttled a pub/priv deps PR, so lets do it all the time.
diff: @@ -983,7 +983,12 @@ fn find_candidate(
  .any(|c| *c == ConflictReason::PublicDependency)
  {
  // we dont have abnormal situations. So we can ask `cx` for how far back we need to go.
  - cx.is_conflicting(Some(parent.package_id()), conflicting_activations)
  + let a = cx.is_conflicting(Some(parent.package_id()), conflicting_activations);
  + // If the `conflicting_activations` does not apply to `cx`, then something went very wrong
  + // in building it. But we will just fall back to laboriously trying all possibilities witch
  + // will give us the correct answer so only `assert` if there is a developer to debug it.
  + debug_assert!(a.is_some());
  + a
  } else {
  None
  };
  