即使我这样做，我也会遇到这个错误：
rake db:drop db:create db:migrate db:seed RAILS_ENV=development
我在OS X上使用rvm ruby 2.2运行rails 4.2
查看我的迁移状态：
devhost:dss jony$ rake db:migrate:status RAILS_ENV=development
database: /Users/jony/dev/rails/dss/db/development.sqlite3
Status Migration ID Migration Name
--------------------------------------------------
up 20150119104811 Create tipo contratos
up 20150119104837 Create docentes
up 20150119105018 Create categoria
up 20150119111856 Create ucs
up 20150119113429 Create departamentos
up 20150119113737 Create ano lectivos
up 20150119113933 Create previsoes
up 20150119115345 Create cursos
up 20150119120602 Create curso ucs
up 20150119151914 Devise create users
up 20150119154317 Create areas
up 20150119154735 Create atribuicoes
up 20150121174741 Devise create admin users
up 20150121174822 Create active admin comments
devhost:dss jony$
那么，这有什么问题？
此致 法比奥