fix(retrofit): Change RetrofitError to SpinnakerServerException

Signed-off-by: benjamin-j-powell <benjamin_j_powell@apple.com>

igor-web/src/main/groovy/com/netflix/spinnaker/igor/jenkins/JenkinsBuildMonitor.groovy

@@ -35,6 +35,9 @@ import com.netflix.spinnaker.igor.polling.PollingDelta
 import com.netflix.spinnaker.igor.service.BuildServices
 import com.netflix.spinnaker.kork.discovery.DiscoveryStatusListener
 import com.netflix.spinnaker.kork.dynamicconfig.DynamicConfigService
+import com.netflix.spinnaker.kork.exceptions.SpinnakerException
+import com.netflix.spinnaker.kork.retrofit.exceptions.SpinnakerServerException
+import com.netflix.spinnaker.kork.retrofit.exceptions.UpstreamBadRequest
 import com.netflix.spinnaker.security.AuthenticatedRequest
 import groovy.time.TimeCategory
 import org.springframework.beans.factory.annotation.Autowired
@@ -157,9 +160,11 @@ class JenkinsBuildMonitor extends CommonPollingMonitor<JobDelta, JobPollingDelta
 
         } catch (e) {
             log.error("Error processing builds for [{}:{}]", kv("master", master), kv("job", job.name), e)
-            if (e.cause instanceof RetrofitError) {
-                def re = (RetrofitError) e.cause
-                log.error("Error communicating with jenkins for [{}:{}]: {}", kv("master", master), kv("job", job.name), kv("url", re.url), re)
+            if (e instanceof SpinnakerServerException) {
+                def re =  e.getRetrofitError();
+                if (re != null) {
+                    log.error("Error communicating with jenkins for [{}:{}]: {}", kv("master", master), kv("job", job.name), kv("url", re.url), re)
+                }
             }
         }
     }