doc: behavior of layers on kres.FAIL in lua modules

modules/README.rst

@@ -118,6 +118,10 @@ doesn't provide any layer to capture events. The Lua module can however provide
 			end 
 	}
 
+There is currently an additional "feature" in comparison to C layer functions:
+the ``consume``, ``produce`` and ``checkout`` functions do not get called at all
+if ``state == kres.FAIL`` (note that ``finish`` does get called nevertheless).
+
 Since the modules are like any other Lua modules, you can interact with them through the CLI and and any interface.
 
 .. tip:: The module can be placed anywhere in the Lua search path, in the working directory or in the MODULESDIR.