[CLIENT] Fixed, that ServerError inherits from Transport::Error

Allow rescuing raised Errors::NotFound or Errors::ServerError by rescue
Transport::Error.

Behavior is now in line with documentation: “The highest-level
exception is {Elasticsearch::Transport::Transport::Error} and will be
raised for any generic client or server errors.”

Closes #100

Author: mlangenberg

elasticsearch-transport/lib/elasticsearch/transport/transport/errors.rb

@@ -12,7 +12,7 @@ class SnifferTimeoutError < Timeout::Error; end
 
       # Elasticsearch server error (HTTP status 5xx)
       #
-      class ServerError < StandardError; end
+      class ServerError < Error; end
 
       module Errors; end
 

elasticsearch-transport/test/unit/transport_base_test.rb

@@ -452,4 +452,9 @@ def initialize(*); end
     end
   end
 
+  context "errors" do
+    should "raise highest-level Error exception for any ServerError" do
+      assert_kind_of Elasticsearch::Transport::Transport::Error, Elasticsearch::Transport::Transport::ServerError.new
+    end
+  end
 end