Provide unexpected error code in error message

lib/tracker_api/client.rb

@@ -223,10 +223,11 @@ def request(method, options = {})
       end
       response
     rescue Faraday::Error::ClientError => e
-      case e.response[:status]
+      status_code = e.response[:status]
+      case status_code
       when 400..499 then raise TrackerApi::Errors::ClientError.new(e)
       when 500..599 then raise TrackerApi::Errors::ServerError.new(e)
-      else raise "Expected 4xx or 5xx HTTP status code"
+      else raise "Expected 4xx or 5xx HTTP status code; got #{status_code} instead."
       end
     end