Raise here instead of a warning.

Gemfile.lock

@@ -43,6 +43,7 @@ GEM
     addressable (2.2.4)
     arel (2.0.8)
     bcrypt-ruby (2.1.4)
+    bcrypt-ruby (2.1.4-java)
     bson (1.2.1)
     bson_ext (1.2.1)
     builder (2.1.2)
@@ -145,6 +146,7 @@ PLATFORMS
 
 DEPENDENCIES
   activerecord-jdbcsqlite3-adapter
+  bcrypt-ruby (~> 2.1.2)
   bson_ext (= 1.2.1)
   devise!
   mocha
@@ -152,7 +154,9 @@ DEPENDENCIES
   mongoid (= 2.0.0.beta.20)
   oa-oauth (~> 0.2.0.beta1)
   oa-openid (~> 0.2.0.beta1)
+  orm_adapter (~> 0.0.3)
   rails (~> 3.0.4)
   ruby-debug (>= 0.10.3)
   sqlite3-ruby
+  warden (~> 1.0.3)
   webrat (= 0.7.2)

lib/devise/omniauth.rb

@@ -6,7 +6,7 @@ rescue LoadError => e
 end
 
 unless OmniAuth.config.respond_to? :test_mode
-  warn "Devise's OmniAuth testing support is deprecated. You should use Omniauth's own support, please ensure you have 0.2.0.beta version or later installed."
+  raise "You are using an old OmniAuth version, please ensure you have 0.2.0.beta version or later installed."
 end
 
 # Clean up the default path_prefix. It will be automatically set by Devise.