Rails 4 Heroku部署错误：预编译资产失败-无法导入/查找boostrap文件

我的应用程序在本地运行；但是，当我尝试将其部署到Heroku时，出现以下错误：

remote:        Sass::SyntaxError: File to import not found or unreadable: bootstrap/dist/css/bootstrap.
remote:        (sass):18
.....
remote:        /tmp/build_c0c6ec9ea8e1ea183aca6e660993c246/vendor/bundle/ruby/2.2.0/gems/sprockets-rails-3.0.1/lib/sprockets/rails/task.rb:67:in `block (2 levels) in define'
remote:        
Sass::SyntaxError: File to import not found or unreadable: bootstrap/dist/css/bootstrap.
.....
remote:        Tasks: TOP => assets:precompile
remote:        (See full trace by running task with --trace)
remote:  !
remote:  !     Precompiling assets failed.
remote:  !

以下是application.scss和Gemfile文件的顺序：

application.scss：

 *= require_self
 *= require custom
 *= require template
 */
 @import "bootstrap-sprockets";
 @import "bootstrap";

宝石文件：

# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '4.2.3'
# Specify Rake version
gem 'rake'
# Use postgresql as the database for Active Record
gem 'pg'
# Use SCSS for stylesheets
gem 'sass-rails', '~> 5.0'
# Use bootstrap sass?
gem 'bootstrap-sass', '>= 3.3.6'
# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'
# Use CoffeeScript for .coffee assets and views
gem 'coffee-rails', '~> 4.1.0'
# See https://github.com/rails/execjs#readme for more supported runtimes
# gem 'therubyracer', platforms: :ruby

# Use jquery as the JavaScript library
gem 'jquery-rails'
# Turbolinks makes following links in your web application faster. Read more: https://github.com/rails/turbolinks
gem 'turbolinks'
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 2.0'
# bundle exec rake doc:rails generates the API under doc/api.
gem 'sdoc', '~> 0.4.0', group: :doc

# For user authentication and registration
gem 'devise'

# Font Awesome and simple form
gem 'simple_form'

# For static pages
gem 'high_voltage'

gem 'paperclip', '~> 3.5.3' # github: 'thoughtbot/paperclip

gem 'closure_tree'

# Use ActiveModel has_secure_password
# gem 'bcrypt', '~> 3.1.7'

# Use Unicorn as the app server
# gem 'unicorn'

# Use Capistrano for deployment
# gem 'capistrano-rails', group: :development

group :development, :test do
  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
  gem 'byebug'

  # Access an IRB console on exception pages or by using <%= console %> in views
  gem 'web-console', '~> 2.0'

  gem 'rspec-rails'
  gem 'capybara'
  gem 'launchy'
end

# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

我的vendor / assets文件夹如下所示：

更新-对我的application.scss所做的更改未推送到Heroku。我以为是因为即使我取出所有需求和导入，Heroku预编译似乎仍然在寻找（而不是寻找）bootstrap！

感谢您的帮助-如果我错过了任何事情，请通知我！

提前致谢。