rb: Add stubs for rake install/package when Echoe not present [THRIFT-52]

Author: Kevin Ballard <kevin@rapleaf.com>


git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@671971 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/rb/Rakefile b/lib/rb/Rakefile
index efd56f7..e88e984 100644
--- a/lib/rb/Rakefile
+++ b/lib/rb/Rakefile
@@ -58,4 +58,10 @@
     p.include_rakefile = true
   end
 rescue LoadError
+  [:install, :package].each do |t|
+    desc "Stub for #{t}"
+    task t do
+      fail "The Echoe gem is required for this task"
+    end
+  end
 end