Show a meaningful error when the DB2 adapter cannot be loaded due to missing dependencies.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@3460 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

@@ -1,5 +1,7 @@
 *SVN*
 
+* Show a meaningful error when the DB2 adapter cannot be loaded due to missing dependencies. [Nicholas Seckar]
+
 * Make .count work for has_many associations with multi line finder sql [schoenm@earthlink.net]
 
 * Add AR::Base.base_class for querying the ancestor AR::Base subclass [Jamis Buck]

activerecord/lib/active_record/connection_adapters/db2_adapter.rb

@@ -219,4 +219,12 @@ begin
   end
 rescue LoadError
   # DB2 driver is unavailable.
+  module ActiveRecord # :nodoc:
+    class Base # :nodoc:
+      def self.db2_connection(config) # :nodoc:
+        # Set up a reasonable error message
+        raise LoadError, "DB2 Libraries could not be loaded."
+      end
+    end
+  end
 end