tweak diagnostics change to mitigate test invalidations

src/composition/learning_networks/nodes.jl

@@ -150,17 +150,18 @@ function _apply(y_plus, input...; kwargs...)
     try
         (y.operation)(mach..., raw_args...)
     catch exception
+        diagnostics = MLJBase.diagnostics(y, input...; kwargs...) # defined in sources.jl
         if !isempty(mach)
             @error "Failed "*
                 "to apply the operation `$(y.operation)` to the machine "*
                 "$(y.machine), which receives it's data arguments from one or more "*
                 "nodes in a learning network. Possibly, one of these nodes "*
-                "is delivering data that is incompatible with the machine's model.\n"
+                "is delivering data that is incompatible "*
+                "with the machine's model.\n"*diagnostics
         else
             @error "Failed "*
-                "to apply the operation `$(y.operation)`."
+                "to apply the operation `$(y.operation)`."*diagnostics
         end
-        @error diagnostics(y, input...; kwargs...) # defined in sources.jl
         rethrow(exception)
     end
 end