データベースの作成について

rake db:create をした際にこのようなエラーが出ます。このエラーはなんでしょうか？

aberyuuryoku-no-MacBook-Air:butelr ryuki$ rake db:create

Couldn't create database for {"adapter"=>"mysql2", "encoding"=>"utf8", "pool"=>5, "username"=>"root", "password"=>nil, "host"=>"localhost", "database"=>"butelr_development"}, {:charset=>"utf8", :collation=>"utf8_unicode_ci"}
(If you set the charset manually, make sure you have a matching collation)

Couldn't create database for {"adapter"=>"mysql2", "encoding"=>"utf8", "pool"=>5, "username"=>"root", "password"=>nil, "host"=>"localhost", "database"=>"butelr_test"}, {:charset=>"utf8", :collation=>"utf8_unicode_ci"}
(If you set the charset manually, make sure you have a matching collation)