How to fix a bundle install "nio4r error" on Rails 5.0.0

Question

The exact error is:

An error occurred while installing nio4r (1.2.1), and bundler cannot continue. Make sure that 'gem install nio4r -v '1.2.1'' succeeds before bundling.

Here is a trace:

Fetching gem metadata from https://rubygems.org/
Fetching version metadata from https://rubygems.org/
Fetching dependency metadata from https://rubygems.org/
Using rake 12.0.0
Using concurrent-ruby 1.0.5
Using i18n 0.8.1
Using minitest 5.10.1
Using thread_safe 0.3.6
Using builder 3.2.3
Using erubis 2.7.0
Using mini_portile2 2.1.0
Using rack 2.0.1
Installing nio4r 1.2.1 with native extensions

Errno::EACCES: Permission denied @ rb_sysopen - /Users/lukeplourde/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/nio4r-1.2.1/.gitignore
Using websocket-extensions 0.1.2
Using mime-types-data 3.2016.0521
Using arel 7.1.4
Using byebug 9.0.6
Using coffee-script-source 1.12.2
Using execjs 2.7.0
Using method_source 0.8.2
Using thor 0.19.4
Using debug_inspector 0.0.2
Using ffi 1.9.17
Using multi_json 1.12.1
Using rb-fsevent 0.9.8
Using puma 3.7.0
Using bundler 1.12.5
Using sass 3.4.23
Using tilt 2.0.6
Using sqlite3 1.3.13
Using turbolinks-source 5.0.0
Using tzinfo 1.2.2
Using nokogiri 1.7.0.1
Using rack-test 0.6.3
Using sprockets 3.7.1
An error occurred while installing nio4r (1.2.1), and Bundler cannot continue.
Make sure that `gem install nio4r -v '1.2.1'` succeeds before bundling.

Answer 1

I was able to fix the problem with:

brew update 

and

bundle update