anchor.diff:  When the call to the remote throws an exception, the cache does not store the result,
   so that a subsequent call to `callRemote()` with the same parameter value will not be
   answered out of the cache.
  -It will instead result in another
  -attempt to call the remote.
  -
  -The previous code example has the side-effect that the cache logs the thrown exception
  -with a long stack trace to the console. This is done to inform developers that something
  -exceptional has happened, but if you have a setup like above, you are already catching
  -the exception and know what you are doing.
  -
  +It will instead result in another attempt to call the remote.
  
positive.code: [#negative-cache]
  == Negative caching and nulls
  
  Sometimes one wants to cache the results of an (expensive) remote call.
  If the remote call fails, one may not want to cache the result or exception,
  but rather re-try the remote call on the next invocation.
  
  
negative.code:     private Integer callRemote(int val)  {
  
          try {
              Integer val = remoteWebServer.getResult(val); //<2>
              return val;
          } catch (Exception e) {
              return null; // <3>
          }
      }
  ----
  