While using rebar3 relup to generate relup file, 
 we noticed if an app is removed from the release,
 the app stop and code purge instructions are ordered before apps which depend on it.

In our case, we have app1 depending on app2,
 in the release which have app2 replaced with app3,
 in the generated relup it instructs to remove app2 before app1 is restarted.
 i.e. app2 is stopped, have all its modules purged, and application unloaded.
 This causes app1 to fail at its stop step because of the dependency.

I am not entirely sure if this is intended or by accident:
 maybe app removals should be ordered the last in the generated instructions?
 i.e. maybe it should be `RU0s ++ RUs` here: 
[https://github.com/erlang/otp/blob/f1ee84f8bb7b642cb5b6b5fd8f96119676c6ffa3/lib/sasl/src/systools_relup.erl#L462]


{code:java}
create_remove_app_scripts(FromRel, ToRel, RU0s, W0s) ->
    RemovedNs = [N || {N, _V, _T} <- FromRel#release.applications,
              not lists:keymember(N, 1, ToRel#release.applications)],
    %% io:format("Removed apps: ~p~n", [RemovedNs]),
    RUs = [[{remove_application, N}] || N <- RemovedNs],
    {RUs ++ RU0s, W0s}.
{code}
edit: updated with a permalink to the line.