NullpointerException in TraceFeignRetryer when using Retryer

[thyzzv]

I'm trying to implement a custom ErrorDecoder that forces a retry on a specific Errorcode.
While trying some options I run into a Nullpointer in TraceFeignRetryer

See thyzzv:sleuthspan-test latest master
Run the example "mvn spring-boot:run"

You will see:
java.lang.NullPointerException: null at org.springframework.cloud.sleuth.instrument.web.client.feign.TraceFeignRetryer.continueOrPropagate(TraceFeignRetryer.java:56) at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:78) at feign.ReflectiveFeign$FeignInvocationHandler.invoke(ReflectiveFeign.java:103) at com.sun.proxy.$Proxy100.exp(Unknown Source) at net.test.sleuth.controllers.SleuthTestController.notOk(SleuthTestController.java:26) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

[marcingrzejszczak]

I think it's high time to do this - #202 cc @spencergibb @adriancole . I'll have to sit down and think on how to add the pre and post process hooks to Feign

[marcingrzejszczak]

Related PR - #367

[marcingrzejszczak]

Should be fixed thanks to #372