Gem::Fetcher::FetchError should receive an uri

The one that failed to be fetched.

bundler/spec/bundler/fetcher/index_spec.rb

@@ -19,7 +19,7 @@
   context "error handling" do
     let(:remote_uri) { Bundler::URI("http://remote-uri.org") }
     before do
-      allow(rubygems).to receive(:fetch_all_remote_specs) { raise Gem::RemoteFetcher::FetchError.new(error_message, nil) }
+      allow(rubygems).to receive(:fetch_all_remote_specs) { raise Gem::RemoteFetcher::FetchError.new(error_message, display_uri) }
       allow(subject).to receive(:remote_uri).and_return(remote_uri)
     end