Vagrant上のRailsプロジェクトでbundle installするとrubygems.orgでエラー

**rails** を起動
`$ rails s`
> **実行結果**
Could not find descendants_tracker-0.0.4 in any of the sources
Run `bundle install` to install missing gems.

**bundle install** をし忘れていたようなので、
`$ bundle install`
> **実行結果**
Fetching source index from https://rubygems.org/
Retrying source fetch due to error (2/3): Bundler::HTTPError Could not fetch specs from https://rubygems.org/
Retrying source fetch due to error (3/3): Bundler::HTTPError Could not fetch specs from https://rubygems.org/
Could not fetch specs from https://rubygems.org/

原因は不明ですが、**rubygems.org** のホスト名が引けてないようです。

**Vagrant** を再起動
`$ vagrant reload`

再び **bundle install**
`$ bundle install`
> **実行結果**
Fetching gem metadata from https://rubygems.org/........
Fetching version metadata from https://rubygems.org/..
Using rake 10.4.2
Using CFPropertyList 2.3.0
Using i18n 0.7.0
Using json 1.8.2
Using minitest 5.5.1
Using thread_safe 0.3.4
Using tzinfo 1.2.2
Using activesupport 4.1.8
Using builder 3.2.2
Using erubis 2.7.0
Using actionview 4.1.8
Using rack 1.5.2
Using rack-test 0.6.3
Using actionpack 4.1.8
Using mime-types 2.4.3
Using mail 2.6.3
Using actionmailer 4.1.8
Using active_decorator 0.4.0
Using activemodel 4.1.8
Using arel 5.0.1.20140414130214
Using activerecord 4.1.8
Using awesome_print 1.6.1
Installing descendants_tracker 0.0.4
Installing ice_nine 0.11.1
Installing axiom-types 0.1.1
Using coderay 1.1.0
Using better_errors 2.1.1
Using debug_inspector 0.0.2
Using binding_of_caller 0.7.2
Using columnize 0.9.0
Using debugger-linecache 1.2.0
Using slop 3.6.0
Using byebug 3.5.1
Using carrierwave 0.10.0
Installing coercible 1.0.0
Using coffee-script-source 1.9.0
Using execjs 2.3.0
Using coffee-script 2.3.0
Using thor 0.19.1
Using railties 4.1.8
Using coffee-rails 4.0.1
Using database_cleaner 1.4.0
Using diff-lcs 1.2.5
Using unf_ext 0.0.6
Using unf 0.1.4
Using domain_name 0.5.23
Using dotenv 1.0.2
Using dotenv-rails 1.0.2
Installing equalizer 0.0.9
Using excon 0.44.2
Using factory_girl 4.5.0
Using factory_girl_rails 4.5.0
Using fission 0.5.0
Using formatador 0.2.5
Using net-ssh 2.9.2
Using net-scp 1.2.1
Using fog-core 1.28.0
Using mini_portile 0.6.2
Using nokogiri 1.6.6.2
Using fog-xml 0.1.1
Using fog-atmos 0.1.0
Using multi_json 1.10.1
Using fog-json 1.0.0
Using ipaddress 0.8.0
Using fog-aws 0.1.0
Using inflecto 0.0.2
Using fog-brightbox 0.7.1
Using fog-ecloud 0.0.2
Using fog-profitbricks 0.0.1
Using fog-radosgw 0.0.3
Using fog-sakuracloud 1.0.0
Using fog-serverlove 0.1.1
Using fog-softlayer 0.4.1
Using fog-storm_on_demand 0.1.0
Using fog-terremark 0.0.4
Using fog-vmfusion 0.0.1
Using fog-voxel 0.0.2
Using fog 1.27.0
Installing hashie 3.4.0
Installing multi_xml 0.5.5
Installing rack-accept 0.4.5
Installing rack-mount 0.8.3
Installing virtus 1.0.4
Installing grape 0.11.0
Using jbuilder 2.2.6
Using tilt 1.4.1
Installing tilt-jbuilder 0.6.1
Installing grape-jbuilder 0.2.0
Using hike 1.2.3
Using http-cookie 1.0.2
Using net-http-digest_auth 1.4
Using net-http-persistent 2.9.4
Using ntlm-http 0.1.1
Using webrobots 0.1.1
Using mechanize 2.7.3
Using bundler 1.8.2
Using sprockets 2.12.3
Using sprockets-rails 2.2.4
Using rails 4.1.8
Using i18n_generators 1.2.1
Using timeliness 0.3.7
Using jc-validates_timeliness 3.1.1
Using jquery-rails 3.1.2
Using kaminari 0.16.2
Installing kgio 2.9.3
Using libv8 3.16.14.7
Using method_source 0.8.2
Using paranoia 2.1.0
Using pg 0.18.1
Using polyamorous 1.1.0
Using pry 0.10.1
Using pry-byebug 3.0.1
Using pry-rails 0.3.3
Using quiet_assets 1.1.0
Using woothee 1.0.1
Using rack-user_agent 0.2.3
Installing raindrops 0.13.0
Using ransack 1.6.3
Using rb-readline 0.5.2
Using rdoc 4.2.0
Using redcarpet 3.2.0 from git://github.com/vmg/redcarpet.git (at master)
Using ref 1.0.5
Using rmagick 2.13.4
Using rspec-support 3.2.1
Using rspec-core 3.2.0
Using rspec-expectations 3.2.0
Using rspec-mocks 3.2.0
Using rspec-rails 3.2.0
Using sass 3.2.19
Using sass-rails 4.0.5
Using sdoc 0.4.1
Using spring 1.3.1
Using spring-commands-rspec 1.0.4
Using therubyracer 0.12.1
Using uglifier 2.7.0
Installing unicorn 4.8.3
Bundle complete! 37 Gemfile dependencies, 136 gems now installed.
Use `bundle show [gemname]` to see where a bundled gem is installed.

無事に **bundle install** できました。