Heroku运行rake db：迁移错误，“没有这样的文件加载 – bundler / setup”

我正在尝试做一个“heroku run rake db：migrate”，并收到此错误：

es-MacBook-Pro:project e$ heroku run rake db:migrate Running rake db:migrate attached to terminal... up, run.1 (in /app) rake aborted! no such file to load -- bundler/setup :29:in `require' :29:in `require' /app/config/boot.rb:6:in `' :29:in `require' :29:in `require' /app/config/application.rb:1:in `' :29:in `require' :29:in `require' /app/Rakefile:5:in `' /usr/local/lib/ruby/1.9.1/rake.rb:2373:in `load' /usr/local/lib/ruby/1.9.1/rake.rb:2373:in `raw_load_rakefile' /usr/local/lib/ruby/1.9.1/rake.rb:2007:in `block in load_rakefile' /usr/local/lib/ruby/1.9.1/rake.rb:2058:in `standard_exception_handling' /usr/local/lib/ruby/1.9.1/rake.rb:2006:in `load_rakefile' /usr/local/lib/ruby/1.9.1/rake.rb:1991:in `run' /usr/local/bin/rake:31:in `' 

我不知道如何解释这个错误。 有没有人有任何线索？