An error occurred while installing bcrypt (3.1.11), and Bundler cannot continue. – Twitter API

I tried to deploy my project with using capistrano, but it was not working.

the error says,

 An error occurred while installing bcrypt (3.1.11), and Bundler cannot
 continue. Make sure that `gem install bcrypt -v '3.1.11'` succeeds
 before bundling.

Here is my error.

INFO [c11e0369] Running $HOME/.rbenv/bin/rbenv exec bundle install --path /var/www/peace/shared/bundle --without development test --deployment --quiet as [email protected]
DEBUG [c11e0369] Command: cd /var/www/peace/releases/20160511092524 && ( export RBENV_ROOT="$HOME/.rbenv" RBENV_VERSION="2.1.7" ; $HOME/.rbenv/bin/rbenv exec bundle install --path /var/www/peace/shared/bundle --without development test --deployment --quiet )
DEBUG [c11e0369]    An error occurred while installing bcrypt (3.1.11), and Bundler cannot continue.
Make sure that `gem install bcrypt -v '3.1.11'` succeeds before bundling.
(Backtrace restricted to imported tasks)
cap aborted!
SSHKit::Runner::ExecuteError: Exception while executing as [email protected]: bundle exit status: 5
bundle stdout: An error occurred while installing bcrypt (3.1.11), and Bundler cannot continue.
Make sure that `gem install bcrypt -v '3.1.11'` succeeds before bundling.
bundle stderr: Nothing written

I don’t have bcript in my gem file.
Here is my Gem file

source 'https://rubygems.org'


# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '4.2.0'
# Use sqlite3 as the database for Active Record
group :development, :test do
  gem 'sqlite3'
end



group :production do
  gem 'mysql2', '~> 0.3.20'
end

# Use SCSS for stylesheets
gem 'bootstrap-datetimepicker-rails'
gem 'bootstrap-timepicker-rails'
gem 'awesome_nested_fields'
gem 'sass-rails', '~> 5.0'
gem 'kaminari'
gem 'whenever', require: false
# 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'
gem 'google-analytics-rails'
gem 'sitemap_generator'
gem 'rails-i18n'
# See https://github.com/sstephenson/execjs#readme for more supported runtimes
#gem 'therubyracer', platforms: :ruby
gem 'rails_admin'
gem 'rails_admin_tag_list'#, :git => 'git://github.com/imouaddine/rails_admin_tag_list.git', :ref => 'a9a4e31af6fdd2124110d0dff81ab97950803e65'
gem 'devise'
gem 'omniauth-twitter'
gem 'omniauth-facebook'
gem 'font-awesome-rails'
gem 'jqplot-rails'
gem 'ransack'
gem 'mail_form'
gem 'simple_form'
gem 'redis', '3.2.2'
gem 'streamio-ffmpeg'


group :production, :staging do

    gem 'unicorn'

end

group :development do
  gem 'capistrano', '~> 3.4.0'
  gem 'capistrano-rails',   '~> 1.1', require: false
  gem 'capistrano-bundler', '~> 1.1', require: false
  gem 'capistrano-rbenv', '~> 2.0', require: false
  gem 'capistrano3-unicorn'
end



# SEO
gem 'meta-tags', :require => 'meta_tags'

gem 'acts-as-taggable-on', '~> 3.4'

gem 'carrierwave'
gem 'rmagick'
gem 'fog'
# Use jquery as the JavaScript library
gem 'jquery-rails'
gem 'jquery-ui-rails'
# Turbolinks makes following links in your web application faster. Read more: https://github.com/rails/turbolinks
gem 'turbolinks'
gem 'jquery-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

# Use ActiveModel has_secure_password


# 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'
  gem 'pry'
  gem 'pry-doc'
  gem 'pry-byebug'
  gem 'pry-rails'
  gem 'awesome_print'
  gem 'bullet'

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

  # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
  gem 'spring'


end

Does anyone know how can I solve this?

Thanks