Update to RubyGems 1.3.7.pre.1

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@27441 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/rubygems/errors.rb

@@ -0,0 +1,35 @@
+class Gem::ErrorReason; end
+
+# Generated when trying to lookup a gem to indicate that the gem
+# was found, but that it isn't usable on the current platform.
+#
+# fetch and install read these and report them to the user to aid
+# in figuring out why a gem couldn't be installed.
+#
+class Gem::PlatformMismatch < Gem::ErrorReason
+
+  attr_reader :name
+  attr_reader :version
+  attr_reader :platforms
+
+  def initialize(name, version)
+    @name = name
+    @version = version
+    @platforms = []
+  end
+
+  def add_platform(platform)
+    @platforms << platform
+  end
+
+  def wordy
+    prefix = "Found #{@name} (#{@version})"
+
+    if @platforms.size == 1
+      "#{prefix}, but was for platform #{@platforms[0]}"
+    else
+      "#{prefix}, but was for platforms #{@platforms.join(' ,')}"
+    end
+  end
+
+end