Log: A shell script for ruby bundler seems to ignore a default ruby version set by rvm. In this case, it had a ruby-1.8 hard-wired in /usr/bin/bundler. I had to uninstall and install bundler to get it fixed.

ruby_bundler_version_inconsistency.log

hig$cat Gemfile
source 'https://rubygems.org'

gem "git-scribe", :git => "https://github.com/eee-c/git-scribe.git", :branch => "breakable-code-blocks"
hig$bundle install
Fetching gem metadata from https://rubygems.org/.........
Fetching gem metadata from https://rubygems.org/..
Fetching https://github.com/eee-c/git-scribe.git
remote: Counting objects: 2017, done.
remote: Compressing objects: 100% (932/932), done.
remote: Total 2017 (delta 1037), reused 2017 (delta 1037)
Receiving objects: 100% (2017/2017), 2.15 MiB | 529.00 KiB/s, done.
Resolving deltas: 100% (1037/1037), done.
Enter your password to install the bundled RubyGems to your system:
Installing liquid (2.6.0)
Gem::InstallError: liquid requires RubyGems version >= 1.3.7. Try 'gem update --system' to update RubyGems itself.
An error occurred while installing liquid (2.6.0), and Bundler cannot continue.
Make sure that `gem install liquid -v '2.6.0'` succeeds before bundling.
hig$sudo gem update --system
Latest version currently installed. Aborting.
hig$sudo bundle list
Gems included by the bundle:
Could not find liquid-2.6.0 in any of the sources
hig$gem install liquid -v '2.6.0'
ERROR:  While executing gem ... (Gem::FilePermissionError)
    You don't have write permissions for the /Library/Ruby/Gems/2.0.0 directory.
hig$bundle list
Gems included by the bundle:
Could not find liquid-2.6.0 in any of the sources
hig$gem --version
2.2.2
hig$head `which bundle`
#!/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby
#
# This file was generated by RubyGems.
#
# The application 'bundler' is installed as part of a gem, and
# this file is here to facilitate running it.
#

require 'rubygems'

hig$gem install liquid
Fetching: liquid-2.6.1.gem (100%)
ERROR:  While executing gem ... (Gem::FilePermissionError)
    You don't have write permissions for the /Library/Ruby/Gems/2.0.0 directory.
hig$sudo gem install liquid
Password:
Fetching: liquid-2.6.1.gem (100%)
Successfully installed liquid-2.6.1
Parsing documentation for liquid-2.6.1
Installing ri documentation for liquid-2.6.1
1 gem installed
hig$head `which bundle`
#!/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby
#
# This file was generated by RubyGems.
#
# The application 'bundler' is installed as part of a gem, and
# this file is here to facilitate running it.
#

require 'rubygems'

hig$which bundle
/usr/bin/bundle
hig$sudo gem uninstall bundler
hig$sudo gem install bundler
Fetching: bundler-1.5.3.gem (100%)
Successfully installed bundler-1.5.3
Parsing documentation for bundler-1.5.3
Installing ri documentation for bundler-1.5.3
1 gem installed
hig$head `which bundle`
#!/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby
#
# This file was generated by RubyGems.
#
# The application 'bundler' is installed as part of a gem, and
# this file is here to facilitate running it.
#

require 'rubygems'

hig$which bundle
hig$bundle install
Fetching gem metadata from https://rubygems.org/.........
Fetching additional metadata from https://rubygems.org/..
Using liquid (2.6.0)
Installing mini_portile (0.5.2)
Installing nokogiri (1.6.0)
Using git-scribe (0.1.1) from https://github.com/eee-c/git-scribe.git (at breakable-code-blocks)
Using bundler (1.5.3)
Your bundle is complete!
Use `bundle show [gemname]` to see where a bundled gem is installed.
hig$