I cannot express my abject frustration at times with the Ruby ecosystem in general and bundler in particular. When you hit this bug:

Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    current directory: /usr/local/rvm/gems/ruby-2.3.1/gems/json-1.8.1/ext/json/ext/generator
/usr/local/rvm/rubies/ruby-2.3.1/bin/ruby -r ./siteconf20161011-22175-140avvd.rb extconf.rb
creating Makefile

current directory: /usr/local/rvm/gems/ruby-2.3.1/gems/json-1.8.1/ext/json/ext/generator
make "DESTDIR=" clean

current directory: /usr/local/rvm/gems/ruby-2.3.1/gems/json-1.8.1/ext/json/ext/generator
make "DESTDIR="
compiling generator.c
In file included from generator.c:1:0:
../fbuffer/fbuffer.h: In function ‘fbuffer_to_s’:
../fbuffer/fbuffer.h:175:47: error: macro "rb_str_new" requires 2 arguments, but only 1 given
     VALUE result = rb_str_new(FBUFFER_PAIR(fb));
                                               ^
../fbuffer/fbuffer.h:175:20: warning: initialization makes integer from pointer without a cast [enabled by default]
     VALUE result = rb_str_new(FBUFFER_PAIR(fb));
                    ^
make: *** [generator.o] Error 1

make failed, exit code 2

Gem files will remain installed in /usr/local/rvm/gems/ruby-2.3.1/gems/json-1.8.1 for inspection.
Results logged to /usr/local/rvm/gems/ruby-2.3.1/extensions/x86_64-linux/2.3.0/json-1.8.1/gem_make.out

An error occurred while installing json (1.8.1), and Bundler cannot continue.
Make sure that `gem install json -v '1.8.1'` succeeds before bundling.

I’ve hit this error, I suspect, a few hundred times and I always forget the solution. And I’m not the only one. Dv and I hit this together today and we shot about 20 minutes today to need this:

gem install json -v1.8.3

Thank you Stack Overflow for this answer. Even if it was buried so deep in the thread that I almost missed it.