jekyll-redirect-from required in order to run `jekyll build`

Received the following error while setting up the site locally: Dependency Error: Yikes! It looks like you don't have jekyll-redirect-from or one of its dependencies installed. I'm including the full stream-of-command-line-consciousness at the bottom of this post, which shows that once the additional gem was installed, jekyll build ran successfully.
Software Versions: ruby 2.6.3p62 jekyll 4.0.0 gem 3.0.3 clang 11.0.0

sudo gem install jekyll
Password:
Fetching http_parser.rb-0.6.0.gem
Fetching public_suffix-4.0.3.gem
Fetching addressable-2.7.0.gem
Fetching em-websocket-0.5.1.gem
Fetching i18n-1.8.2.gem
Fetching colorator-1.1.0.gem
Fetching concurrent-ruby-1.1.6.gem
Fetching eventmachine-1.2.7.gem
Fetching ffi-1.12.2.gem
Fetching sassc-2.2.1.gem
Fetching jekyll-sass-converter-2.1.0.gem
Fetching rb-fsevent-0.10.3.gem
Fetching rb-inotify-0.10.1.gem
Fetching listen-3.2.1.gem
Fetching jekyll-watch-2.2.1.gem
Fetching kramdown-2.1.0.gem
Fetching kramdown-parser-gfm-1.1.0.gem
Fetching liquid-4.0.3.gem
Fetching mercenary-0.3.6.gem
Fetching forwardable-extended-2.6.0.gem
Fetching pathutil-0.16.2.gem
Fetching rouge-3.17.0.gem
Fetching safe_yaml-1.0.5.gem
Fetching unicode-display_width-1.7.0.gem
Fetching terminal-table-1.8.0.gem
Fetching jekyll-4.0.0.gem
Successfully installed public_suffix-4.0.3
Successfully installed addressable-2.7.0
Successfully installed colorator-1.1.0
Building native extensions. This could take a while...
Successfully installed http_parser.rb-0.6.0
Building native extensions. This could take a while...
Successfully installed eventmachine-1.2.7
Successfully installed em-websocket-0.5.1
Successfully installed concurrent-ruby-1.1.6

HEADS UP! i18n 1.1 changed fallbacks to exclude default locale.
But that may break your application.

If you are upgrading your Rails application from an older version of Rails:

Please check your Rails app for 'config.i18n.fallbacks = true'.
If you're using I18n (>= 1.1.0) and Rails (< 5.2.2), this should be
'config.i18n.fallbacks = [I18n.default_locale]'.
If not, fallbacks will be broken in your app by I18n 1.1.x.

If you are starting a NEW Rails application, you can ignore this notice.

For more info see:
https://github.com/svenfuchs/i18n/releases/tag/v1.1.0

Successfully installed i18n-1.8.2
Building native extensions. This could take a while...
Successfully installed ffi-1.12.2
Building native extensions. This could take a while...
Successfully installed sassc-2.2.1
Successfully installed jekyll-sass-converter-2.1.0
Successfully installed rb-fsevent-0.10.3
Successfully installed rb-inotify-0.10.1
Successfully installed listen-3.2.1
Successfully installed jekyll-watch-2.2.1
Successfully installed kramdown-2.1.0
Successfully installed kramdown-parser-gfm-1.1.0
Successfully installed liquid-4.0.3
Successfully installed mercenary-0.3.6
Successfully installed forwardable-extended-2.6.0
Successfully installed pathutil-0.16.2
Successfully installed rouge-3.17.0
Successfully installed safe_yaml-1.0.5
Successfully installed unicode-display_width-1.7.0
Successfully installed terminal-table-1.8.0
-------------------------------------------------------------------------------------
Jekyll 4.0 comes with some major changes, notably:

  * Our `link` tag now comes with the `relative_url` filter incorporated into it.
    You should no longer prepend `{{ site.baseurl }}` to `{% link foo.md %}`
    For further details: https://github.com/jekyll/jekyll/pull/6727

  * Our `post_url` tag now comes with the `relative_url` filter incorporated into it.
    You shouldn't prepend `{{ site.baseurl }}` to `{% post_url 2019-03-27-hello %}`
    For further details: https://github.com/jekyll/jekyll/pull/7589

  * Support for deprecated configuration options has been removed. We will no longer
    output a warning and gracefully assign their values to the newer counterparts
    internally.
-------------------------------------------------------------------------------------
Successfully installed jekyll-4.0.0
Parsing documentation for public_suffix-4.0.3
Installing ri documentation for public_suffix-4.0.3
Parsing documentation for addressable-2.7.0
Installing ri documentation for addressable-2.7.0
Parsing documentation for colorator-1.1.0
Installing ri documentation for colorator-1.1.0
Parsing documentation for http_parser.rb-0.6.0
unknown encoding name "chunked\r\n\r\n25" for ext/ruby_http_parser/vendor/http-parser-java/tools/parse_tests.rb, skipping
Installing ri documentation for http_parser.rb-0.6.0
Parsing documentation for eventmachine-1.2.7
Installing ri documentation for eventmachine-1.2.7
Parsing documentation for em-websocket-0.5.1
Installing ri documentation for em-websocket-0.5.1
Parsing documentation for concurrent-ruby-1.1.6
Installing ri documentation for concurrent-ruby-1.1.6
Parsing documentation for i18n-1.8.2
Installing ri documentation for i18n-1.8.2
Parsing documentation for ffi-1.12.2
Installing ri documentation for ffi-1.12.2
Parsing documentation for sassc-2.2.1
Installing ri documentation for sassc-2.2.1
Parsing documentation for jekyll-sass-converter-2.1.0
Installing ri documentation for jekyll-sass-converter-2.1.0
Parsing documentation for rb-fsevent-0.10.3
Installing ri documentation for rb-fsevent-0.10.3
Parsing documentation for rb-inotify-0.10.1
Installing ri documentation for rb-inotify-0.10.1
Parsing documentation for listen-3.2.1
Installing ri documentation for listen-3.2.1
Parsing documentation for jekyll-watch-2.2.1
Installing ri documentation for jekyll-watch-2.2.1
Parsing documentation for kramdown-2.1.0
Installing ri documentation for kramdown-2.1.0
Parsing documentation for kramdown-parser-gfm-1.1.0
Installing ri documentation for kramdown-parser-gfm-1.1.0
Parsing documentation for liquid-4.0.3
Installing ri documentation for liquid-4.0.3
Parsing documentation for mercenary-0.3.6
Installing ri documentation for mercenary-0.3.6
Parsing documentation for forwardable-extended-2.6.0
Installing ri documentation for forwardable-extended-2.6.0
Parsing documentation for pathutil-0.16.2
Installing ri documentation for pathutil-0.16.2
Parsing documentation for rouge-3.17.0
Installing ri documentation for rouge-3.17.0
Parsing documentation for safe_yaml-1.0.5
Installing ri documentation for safe_yaml-1.0.5
Parsing documentation for unicode-display_width-1.7.0
Installing ri documentation for unicode-display_width-1.7.0
Parsing documentation for terminal-table-1.8.0
Installing ri documentation for terminal-table-1.8.0
Parsing documentation for jekyll-4.0.0
Installing ri documentation for jekyll-4.0.0
Done installing documentation for public_suffix, addressable, colorator, http_parser.rb, eventmachine, em-websocket, concurrent-ruby, i18n, ffi, sassc, jekyll-sass-converter, rb-fsevent, rb-inotify, listen, jekyll-watch, kramdown, kramdown-parser-gfm, liquid, mercenary, forwardable-extended, pathutil, rouge, safe_yaml, unicode-display_width, terminal-table, jekyll after 35 seconds
26 gems installed
aronlurie@nason codeforboston.org % jekyll build
Configuration file: /Users/aronlurie/codeforboston.org/_config.yml
  Dependency Error: Yikes! It looks like you don't have jekyll-redirect-from or one of its dependencies installed. In order to use Jekyll as currently configured, you'll need to install this gem. If you've run Jekyll with `bundle exec`, ensure that you have included the jekyll-redirect-from gem in your Gemfile as well. The full error message from Ruby is: 'cannot load such file -- jekyll-redirect-from' If you run into trouble, you can find helpful resources at https://jekyllrb.com/help/! 
                    ------------------------------------------------
      Jekyll 4.0.0   Please append `--trace` to the `build` command 
                     for any additional information or backtrace. 
                    ------------------------------------------------
aronlurie@nason codeforboston.org % ls
CNAME           _rooms          favicon.png     ndoch.html
LICENSE         _sass           hackathon.html      old_ndoch.html
_config.yml     about.html      hacknight.html      projects.html
_data           code-of-conduct.md  img         readme.md
_includes       css         index.html      style_guide.html
_layouts        event.html      js          tools.html
aronlurie@nason codeforboston.org % ls -a
.           _data           event.html      old_ndoch.html
..          _includes       favicon.png     projects.html
.git            _layouts        hackathon.html      readme.md
.gitignore      _rooms          hacknight.html      style_guide.html
.jekyll-cache       _sass           img         tools.html
CNAME           about.html      index.html
LICENSE         code-of-conduct.md  js
_config.yml     css         ndoch.html
aronlurie@nason codeforboston.org % sudo gem install jekyll-redirect-from
Fetching jekyll-redirect-from-0.16.0.gem
Successfully installed jekyll-redirect-from-0.16.0
Parsing documentation for jekyll-redirect-from-0.16.0
Installing ri documentation for jekyll-redirect-from-0.16.0
Done installing documentation for jekyll-redirect-from after 0 seconds
1 gem installed
aronlurie@nason codeforboston.org % jekyll build                         
Configuration file: /Users/aronlurie/codeforboston.org/_config.yml
            Source: /Users/aronlurie/codeforboston.org
       Destination: /Users/aronlurie/codeforboston.org/_site
 Incremental build: disabled. Enable with --incremental
      Generating... 
                    done in 0.092 seconds.
 Auto-regeneration: disabled. Use --watch to enable.
aronlurie@nason codeforboston.org % jekyll serve --livereload
Configuration file: /Users/aronlurie/codeforboston.org/_config.yml
            Source: /Users/aronlurie/codeforboston.org
       Destination: /Users/aronlurie/codeforboston.org/_site
 Incremental build: disabled. Enable with --incremental
      Generating... ```
codeforboston / codeforboston.org

jekyll-redirect-from required in order to run `jekyll build` #105
