make the running of tasks with script/extension install conditional

lib/radiant/extension/script.rb

@@ -1,6 +1,7 @@
 require 'active_resource'
 require 'tmpdir'
 require 'fileutils'
+require 'rake'
 
 module Registry
   class Extension < ActiveResource::Base
@@ -29,7 +30,17 @@ def inspect
 
   class Action
     def rake(command)
-      `rake #{command} RAILS_ENV=#{RAILS_ENV}`
+      `rake #{command} RAILS_ENV=#{RAILS_ENV}` if tasks_include? command
+    end
+
+    def tasks_include?(command)
+      extension = command.split(':')[2]
+      rake_file = File.join(RAILS_ROOT, 'vendor', 'extensions', extension) + '/lib/tasks/' + extension + '_extension_tasks.rake'
+      if File.exist? rake_file
+        load rake_file
+        tasks = Rake.application.tasks.map(&:name)
+      end
+      tasks.include? "#{command}"
     end
 
     def file_utils