net-http no longer requires stringio

spec/ruby/library/net/http/http/get_spec.rb

@@ -30,6 +30,7 @@ describe "Net::HTTP.get" do
   describe "when reading gzipped contents" do
     def start_threads
       require 'zlib'
+      require 'stringio'
 
       server = nil
       server_thread = Thread.new do

spec/ruby/library/net/http/httpresponse/read_body_spec.rb

@@ -1,5 +1,6 @@
 require_relative '../../../../spec_helper'
 require 'net/http'
+require 'stringio'
 
 describe "Net::HTTPResponse#read_body" do
   before :each do

spec/ruby/library/net/http/httpresponse/read_new_spec.rb

@@ -1,5 +1,6 @@
 require_relative '../../../../spec_helper'
 require 'net/http'
+require 'stringio'
 
 describe "Net::HTTPResponse.read_new" do
   it "creates a HTTPResponse object based on the response read from the passed socket" do

spec/ruby/library/net/http/httpresponse/shared/body.rb

@@ -1,3 +1,5 @@
+require 'stringio'
+
 describe :net_httpresponse_body, shared: true do
   before :each do
     @res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")