No Relays related error crashes

[vanstee]

If you try to run a command in a bundle assigned to a relay group that contains a relay that isn't currently running you'll receive the following stacktrace from the executor. Seems like a simple function head went missing.

** (FunctionClauseError) no function clause matching in Cog.Pipeline.Errors.lookup/1
    (cog) lib/cog/pipeline/errors.ex:7: Cog.Pipeline.Errors.lookup(%Cog.Pipeline.DoneSignal{bundle_version_id: nil, error: {:error, :no_relays}, invocation: nil, template: nil})
    (cog) lib/cog/pipeline/error_sink.ex:131: Cog.Pipeline.ErrorSink.prepare_error_context/2
    (cog) lib/cog/pipeline/error_sink.ex:108: Cog.Pipeline.ErrorSink.send_to_adapter/3
    (elixir) lib/enum.ex:657: anonymous fn/3 in Enum.each/2
    (stdlib) lists.erl:1263: :lists.foldl/3
    (elixir) lib/enum.ex:656: Enum.each/2
    (elixir) lib/enum.ex:651: Enum."-each/2-lists^foreach/1-0-"/2
    (elixir) lib/enum.ex:651: Enum.each/2