Rubyonrails Heroku 推送被拒绝，无法通过 Bundler 安装 gem

我正在努力将我的代码推送到Heroku.在谷歌和堆栈溢出问题上搜索之后，我一直无法找到解决方案.以下是我try "git push heroku master"时得到的结果:

Heroku receiving push
-----> Rails app detected
-----> Detected Rails is not set to serve static_assets
       Installing rails3_serve_static_assets... done
-----> Gemfile detected, running Bundler version 1.0.3
       Unresolved dependencies detected; Installing...
       Fetching source index for http://rubygems.org/
       /usr/ruby1.8.7/lib/ruby/site_ruby/1.8/rubygems/remote_fetcher.rb:300:in `open_uri_or_path': bad response Not Found 404 (http://rubygems.org/quick/Marshal.4.8/mail-2.2.6.001.gemspec.rz) (Gem::RemoteFetcher::FetchError)
        from /usr/ruby1.8.7/lib/ruby/site_ruby/1.8/rubygems/remote_fetcher.rb:172:in `fetch_path'
.
....

最后:

FAILED: http://docs.heroku.com/bundler
 !     Heroku push rejected, failed to install gems via Bundler

error: hooks/pre-receive exited with error code 1
To git@heroku.com:myapp.git
 ! [remote rejected] master -> master (pre-receive hook declined)
error: failed to push some refs to 'git@heroku.com:myapp.git'

谢谢你的帮助！