anchor.diff:          {ok, JsonRes} ->
               {ok, JsonRes};
           {error, Error} ->
  +            lager:debug("Get key pair error: ~p", [Error]),
               {error, Error}
       end.
   
  
positive.code:     case libcloud_wrapper(JsonInput) of
          {ok, JsonRes} ->
              {ok, JsonRes};
          {error, _} = Error ->
              Error
      end.
  
  %%------------------------------------------------------------------------------
  
negative.code: 
              case MatchingNodes of
                  [] ->
                      lager:debug("Node getting error (NodeId=~p): no such node"),
                      {error, {no_such_node, [{<<"id">>, BinNodeId}]}};
                  [Node] ->
                      Node;
                  _ when is_list(MatchingNodes) ->
                      % This can happen only if the cloud provider is buggy,
                      % that's why it is not reported in the type spec.
                      lager:debug("Node getting error (NodeId=~p): multiple "
                                  "nodes"),
                      {error, {multiple_nodes, [{<<"id">>, BinNodeId}]}}
              end;
          {error, Error} ->
              % debug log printed by list_nodes call
              {error, Error}
      end.
  
  