Running `bundle install` as non-root user causes `rake` to be not found

/mesos/site /mesos
Fetching gem metadata from https://rubygems.org/............
Fetching version metadata from https://rubygems.org/..
Fetching dependency metadata from https://rubygems.org/.
Rubygems 2.0.14.1 is not threadsafe, so your gems will be installed one at a time. Upgrade to Rubygems 2.1.0 or higher to enable parallel gem installation.
Fetching rake 12.0.0
Installing rake 12.0.0
Fetching i18n 0.6.11
Installing i18n 0.6.11
Fetching multi_json 1.12.1
Installing multi_json 1.12.1
Fetching addressable 2.3.8
Installing addressable 2.3.8
Using bundler 1.15.3
Fetching chunky_png 1.3.8
Installing chunky_png 1.3.8
Fetching coffee-script-source 1.12.2
Installing coffee-script-source 1.12.2
Fetching sass 3.4.24
Installing sass 3.4.24
Fetching rb-fsevent 0.10.2
Installing rb-fsevent 0.10.2
Fetching ffi 1.9.18
Installing ffi 1.9.18 with native extensions
Fetching eventmachine 1.2.3
Installing eventmachine 1.2.3 with native extensions
Fetching http_parser.rb 0.6.0
Installing http_parser.rb 0.6.0 with native extensions
Fetching temple 0.8.0
Installing temple 0.8.0
Fetching tilt 1.3.7
Installing tilt 1.3.7
Fetching hike 1.2.3
Installing hike 1.2.3
Fetching htmlentities 4.3.4
Installing htmlentities 4.3.4
Fetching kramdown 1.14.0
Installing kramdown 1.14.0
Fetching libv8 3.16.14.19 (x86_64-linux)
Installing libv8 3.16.14.19 (x86_64-linux)
Fetching rack 1.6.8
Installing rack 1.6.8
Fetching thor 0.19.4
Installing thor 0.19.4
Fetching thread_safe 0.3.6
Installing thread_safe 0.3.6
Fetching rdiscount 2.1.7
Installing rdiscount 2.1.7 with native extensions
Fetching ref 2.0.0
Installing ref 2.0.0
Fetching activesupport 3.2.22.5
Installing activesupport 3.2.22.5
Fetching execjs 1.4.1
Installing execjs 1.4.1
Fetching compass-core 1.0.3
Installing compass-core 1.0.3
Fetching compass-import-once 1.0.5
Installing compass-import-once 1.0.5
Fetching rb-inotify 0.9.10
Installing rb-inotify 0.9.10
Fetching rb-kqueue 0.2.5
Installing rb-kqueue 0.2.5
Fetching em-websocket 0.5.1
Installing em-websocket 0.5.1
Fetching haml 5.0.1
Installing haml 5.0.1
Fetching rack-test 0.6.3
Installing rack-test 0.6.3
Fetching sprockets 2.12.4
Installing sprockets 2.12.4
Fetching rack-livereload 0.3.16
Installing rack-livereload 0.3.16
Fetching rouge 0.3.10
Installing rouge 0.3.10
Fetching tzinfo 1.2.3
Installing tzinfo 1.2.3
Fetching therubyracer 0.12.3
Installing therubyracer 0.12.3 with native extensions
Fetching coffee-script 2.2.0
Installing coffee-script 2.2.0
Fetching uglifier 2.1.2
Installing uglifier 2.1.2
Fetching compass 1.0.3
Installing compass 1.0.3
Fetching listen 1.3.1
Installing listen 1.3.1
Fetching sprockets-helpers 1.1.0
Installing sprockets-helpers 1.1.0
Fetching sprockets-sass 1.1.0
Installing sprockets-sass 1.1.0
Fetching middleman-core 3.2.0
Installing middleman-core 3.2.0
Fetching middleman-sprockets 3.3.3
Installing middleman-sprockets 3.3.3
Fetching middleman-blog 3.5.1
Installing middleman-blog 3.5.1
Fetching middleman-livereload 3.1.0
Installing middleman-livereload 3.1.0
Fetching middleman-syntax 1.2.1
Installing middleman-syntax 1.2.1
Fetching middleman 3.2.0
Installing middleman 3.2.0
Bundle complete! 8 Gemfile dependencies, 49 gems now installed.
Use `bundle info [gemname]` to see where a bundled gem is installed.
Post-install message from compass:
    Compass is charityware. If you love it, please donate on our behalf at http://umdf.org/compass Thanks!
Post-install message from middleman-core:
NOTICE: Middleman v3.2.x and greater no longer support Ruby 1.8
bundler: command not found: rake
Install missing gem executables with `bundle install`
bundler: command not found: rake
Install missing gem executables with `bundle install`