* lib/rubygems.rb, lib/rubygems/*, test/rubygems/*: Update rubygems-2.6.3.

Please see entries of 2.6.3 on
  https://github.com/rubygems/rubygems/blob/master/History.txt

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54500 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/rubygems/dependency.rb

@@ -286,9 +286,7 @@ class Gem::Dependency
       }
     end
 
-    # `stubs_for` returns oldest first, but `matching_specs` is supposed to
-    # return newest first, so just reverse the list
-    matches.reverse
+    matches
   end
 
   ##
@@ -307,18 +305,10 @@ class Gem::Dependency
       specs = Gem::Specification.stubs_for name
 
       if specs.empty?
-        total = Gem::Specification.stubs.size
-        msg   = "Could not find '#{name}' (#{requirement}) among #{total} total gem(s)\n".dup
+        raise Gem::MissingSpecError.new name, requirement
       else
-        specs = specs.map(&:full_name)
-        msg   = "Could not find '#{name}' (#{requirement}) - did find: [#{specs.join ','}]\n".dup
+        raise Gem::MissingSpecVersionError.new name, requirement, specs
       end
-      msg << "Checked in 'GEM_PATH=#{Gem.path.join(File::PATH_SEPARATOR)}', execute `gem env` for more information"
-
-      error = Gem::LoadError.new(msg)
-      error.name        = self.name
-      error.requirement = self.requirement
-      raise error
     end
 
     # TODO: any other resolver validations should go here