* lib/rubygems.rb (Gem.load_yaml): return if Kernel#gem is not defined

yet. This causes crash if test-all requires libraries in a certain
  order. A simple reproducible code is
  ruby --disable-gem -e'require"yaml";require"minitest/autorun"'

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@37989 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,10 @@
+Thu Nov 29 17:31:53 2012  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* lib/rubygems.rb (Gem.load_yaml): return if Kernel#gem is not defined
+	  yet. This causes crash if test-all requires libraries in a certain
+	  order. A simple reproducible code is
+	  ruby --disable-gem -e'require"yaml";require"minitest/autorun"'
+
 Thu Nov 29 17:19:26 2012  Eric Hodel  <drbrain@segment7.net>
 
 	* lib/tracer.rb:  Updated to match removal of custom_require from
@@ -34,7 +41,7 @@ Thu Nov 29 16:18:14 2012  Eric Hodel  <drbrain@segment7.net>
 
 	* lib/rubygems/test_case.rb:  Disable loading of keys and certificates
 	  outside rubygems or ruby tests as the files are not available (or
-          necessary).
+	  necessary).
 
 Thu Nov 29 16:14:41 2012  Koichi Sasada  <ko1@atdot.net>
 

lib/rubygems.rb

@@ -536,6 +536,7 @@ module Gem
 
   def self.load_yaml
     return if @yaml_loaded
+    return unless defined?(gem)
 
     test_syck = ENV['TEST_SYCK']