core/utils/logger: Log FetchError's status (#2024)

The standard serializer of Bunyan, our logging library, strips out
most attributes of logged errors which means we can miss some
important information when those include non standard attributes.

For example, the `status` attribute of `FetchError`s are stripped
out so we can't know the returned status of failed requests.
As we've done for other attributes, we add it back to the logged
object.

core/utils/logger.js

@@ -83,6 +83,7 @@ function errSerializer(err) {
     port,
     syscall,
     code,
+    status,
     originalErr
   } = err
 
@@ -95,6 +96,7 @@ function errSerializer(err) {
   if (port) obj.port = port
   if (syscall) obj.syscall = syscall
   if (code) obj.code = code
+  if (status) obj.status = status
   if (originalErr) obj.originalErr = originalErr
 
   return obj