Check ruby version to be >= 2.0.0

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

lib/tasks/gitlab/check.rake

@@ -27,6 +27,7 @@ namespace :gitlab do
       check_projects_have_namespace
       check_satellites_exist
       check_redis_version
+      check_ruby_version
       check_git_version
 
       finished_checking "GitLab"
@@ -816,6 +817,23 @@ namespace :gitlab do
     end
   end
 
+  def check_ruby_version
+    required_version = Gitlab::VersionInfo.new(2, 0, 0)
+    current_version = Gitlab::VersionInfo.parse(run(%W(ruby --version)))
+
+    print "Ruby version >= #{required_version} ? ... "
+
+    if current_version.valid? && required_version <= current_version
+        puts "yes (#{current_version})".green
+    else
+      puts "no".red
+      try_fixing_it(
+        "Update your ruby to a version >= #{required_version} from #{current_version}"
+      )
+      fix_and_rerun
+    end
+  end
+
   def check_git_version
     required_version = Gitlab::VersionInfo.new(1, 7, 10)
     current_version = Gitlab::VersionInfo.parse(run(%W(#{Gitlab.config.git.bin_path} --version)))