lib/rubygems/indexer.rb: suppress random test-all error

by bundler. Similar to r65613, but fixing this more carefully
because here is not just inside tests but inside rubygems code.
http://ci.rvm.jp/results/trunk_gcc5@silicon-docker/1448239

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65629 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/rubygems/indexer.rb

@@ -4,10 +4,17 @@ require 'rubygems/package'
 require 'time'
 require 'tmpdir'
 
+rescue_exceptions = [LoadError]
+begin
+  require 'bundler/errors'
+rescue LoadError # this rubygems + old ruby
+else # this rubygems + ruby trunk with bundler
+  rescue_exceptions << Bundler::GemfileNotFound
+end
 begin
   gem 'builder'
   require 'builder/xchar'
-rescue LoadError
+rescue *rescue_exceptions
 end
 
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