我正在尝试构建一个 docker 容器，但收到以下错误消息：
Step 8/12 : RUN bundle binstubs bundler --force
---> Running in ed94b127974b
Could not find gem 'rails (>= 5.1.5, ~> 5.1)' in any of the gem sources listed
in your Gemfile.
ERROR: Service 'dockerzon' failed to build: The command '/bin/sh -c bundle binstubs bundler --force' returned a non-zero code: 7
我在 Gemfile 中尝试过不同版本的 Rails，但没有成功！这是我的 Gemfile 中的内容：
source 'https://rubygems.org'
# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
# gem 'rails', '4.2.6'
# gem 'rails', '>= 5.1.5'
gem …