rescue LoadError if memcache isn't available while loading the MemCache fragment store

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@7726 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

actionpack/lib/action_controller/caching.rb

@@ -485,6 +485,7 @@ def initialize(address = 'druby://localhost:9192')
         end
       end
 
+    begin
       require_library_or_gem 'memcache'
       class MemCacheStore < MemoryStore #:nodoc:
         attr_reader :addresses
@@ -497,6 +498,9 @@ def initialize(*addresses)
           @data = MemCache.new(*addresses)
         end
       end
+    rescue LoadError
+      # MemCache wasn't available so neither can the store be
+    end
 
       class UnthreadedFileStore #:nodoc:
         attr_reader :cache_path