sqlite3 の環境で database_cleaner 1.1.1 の DatabaseCleaner.clean が postgresql_version の NameError (DatabaseCleaner.strategy = :truncation のとき)

DatabaseCleaner-error.txt

% RAILS_ENV=test rails c
Loading test environment (Rails 4.0.0)
irb(main):001:0> DatabaseCleaner.strategy = :truncation
=> :truncation
irb(main):002:0> DatabaseCleaner.clean
NameError: undefined local variable or method `postgresql_version' for #<ActiveRecord::ConnectionAdapters::SQLite3Adapter:0x007fb69ce84fe0>
        from /Users/kazu/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/database_cleaner-1.1.1/lib/database_cleaner/active_record/truncation.rb:123:in `db_version'
        from /Users/kazu/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/database_cleaner-1.1.1/lib/database_cleaner/active_record/truncation.rb:131:in `restart_identity'
        from /Users/kazu/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/database_cleaner-1.1.1/lib/database_cleaner/active_record/truncation.rb:140:in `truncate_tables'
        from /Users/kazu/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/database_cleaner-1.1.1/lib/database_cleaner/active_record/truncation.rb:234:in `block in clean'
        from /Users/kazu/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/activerecord-4.0.0/lib/active_record/connection_adapters/abstract_adapter.rb:307:in `disable_referential_integrity'
        from /Users/kazu/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/database_cleaner-1.1.1/lib/database_cleaner/active_record/truncation.rb:230:in `clean'
        from /Users/kazu/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/database_cleaner-1.1.1/lib/database_cleaner/base.rb:86:in `clean'
        from /Users/kazu/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/database_cleaner-1.1.1/lib/database_cleaner/configuration.rb:79:in `block in clean'
        from /Users/kazu/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/database_cleaner-1.1.1/lib/database_cleaner/configuration.rb:79:in `each'
        from /Users/kazu/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/database_cleaner-1.1.1/lib/database_cleaner/configuration.rb:79:in `clean'
        from (irb):2
        from /Users/kazu/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/railties-4.0.0/lib/rails/commands/console.rb:90:in `start'
        from /Users/kazu/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/railties-4.0.0/lib/rails/commands/console.rb:9:in `start'
        from /Users/kazu/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/railties-4.0.0/lib/rails/commands.rb:64:in `<top (required)>'
        from bin/rails:4:in `require'
        from bin/rails:4:in `<main>'
irb(main):003:0> ActiveRecord::Base.connection.class.ancestors
=> [ActiveRecord::ConnectionAdapters::SQLite3Adapter, ActiveRecord::ConnectionAdapters::AbstractAdapter, DatabaseCleaner::ActiveRecord::PostgreSQLAdapter, DatabaseCleaner::ActiveRecord::SQLiteAdapter, DatabaseCleaner::ActiveRecord::AbstractAdapter, ActiveRecord::ConnectionAdapters::ColumnDumper, MonitorMixin, ActiveSupport::Callbacks, ActiveRecord::ConnectionAdapters::QueryCache, ActiveRecord::ConnectionAdapters::DatabaseLimits, ActiveRecord::ConnectionAdapters::Quoting, ActiveRecord::ConnectionAdapters::DatabaseStatements, ActiveRecord::ConnectionAdapters::SchemaStatements, ActiveRecord::Migration::JoinTable, Object, PP::ObjectMixin, ActiveSupport::Dependencies::Loadable, JSON::Ext::Generator::GeneratorMethods::Object, Kernel, BasicObject]
irb(main):004:0>