Add a note about ensuring the version is right for the adapter (since you...

Add a note about ensuring the version is right for the adapter (since you might well have specified the right gem, but locked it to too low of a version)

activerecord/lib/active_record/connection_adapters/connection_specification.rb

@@ -55,7 +55,7 @@ def resolve_hash_connection(spec) # :nodoc:
           begin
             require path_to_adapter
           rescue Gem::LoadError => e
-            raise Gem::LoadError, "Specified '#{spec[:adapter]}' for database adapter, but the gem is not loaded. Add `gem '#{e.name}'` to your Gemfile."
+            raise Gem::LoadError, "Specified '#{spec[:adapter]}' for database adapter, but the gem is not loaded. Add `gem '#{e.name}'` to your Gemfile (and ensure its version is at the minimum required by ActiveRecord)."
           rescue LoadError => e
             raise LoadError, "Could not load '#{path_to_adapter}'. Make sure that the adapter in config/database.yml is valid. If you use an adapter other than 'mysql', 'mysql2', 'postgresql' or 'sqlite3' add the necessary adapter gem to the Gemfile.", e.backtrace
           end