bundle is throwing an error while installing dradis community edition

I am trying to install dradis community edition for Kali linux through this website:

https://dradisframework.com/ce/documentation/install_kali.html

and

https://dradisframework.com/ce/documentation/install_git.html

when I run the command:

./bin/setup

I am getting the following error:

== Enabling default add-ons ==
== Installing dependencies ==
Traceback (most recent call last):
    1: from /usr/local/bin/bundle:23:in `<main>'
/usr/local/bin/bundle:23:in `load': cannot load such file -- /usr/share/rubygems-integration/all/gems/bundler-1.17.3/exe/bundle (LoadError)
Traceback (most recent call last):
    1: from /usr/local/bin/bundle:23:in `<main>'
/usr/local/bin/bundle:23:in `load': cannot load such file -- /usr/share/rubygems-integration/all/gems/bundler-1.17.3/exe/bundle (LoadError)

== Command ["bundle install"] failed ==

This is happening on all bundle commands like

bundle -v

bundle install

What could be causing this? I am new to this.

Update 1:

I tried gem update --system and tried the ./bin/setup again. It gives me the following error:

Fetching nokogumbo 2.0.1
Installing nokogumbo 2.0.1 with native extensions
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    current directory: /root/dradis-ce/gems/nokogumbo-2.0.1/ext/nokogumbo
/usr/bin/ruby2.5 -I /usr/local/lib/site_ruby/2.5.0 -r ./siteconf20190224-6660-1caz3w7.rb extconf.rb
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.  Check the mkmf.log file for more details.  You may
need configuration options.

Provided configuration options:
    --with-opt-dir
    --without-opt-dir
    --with-opt-include
    --without-opt-include=${opt-dir}/include
    --with-opt-lib
    --without-opt-lib=${opt-dir}/lib
    --with-make-prog
    --without-make-prog
    --srcdir=.
    --curdir
    --ruby=/usr/bin/$(RUBY_BASE_NAME)2.5
/usr/local/lib/site_ruby/2.5.0/rubygems/dependency.rb:313:in `to_specs': Could not find 'nokogiri' (= 1.8.4) - did find: [nokogiri-1.8.5]
(Gem::MissingSpecVersionError)
Checked in 'GEM_PATH=/root/dradis-ce', execute `gem env` for more information
    from /usr/local/lib/site_ruby/2.5.0/rubygems/dependency.rb:323:in `to_spec'
    from /usr/local/lib/site_ruby/2.5.0/rubygems/specification.rb:1033:in `find_by_name'
    from extconf.rb:9:in `<main>'

extconf failed, exit code 1

Gem files will remain installed in /root/dradis-ce/gems/nokogumbo-2.0.1 for inspection.
Results logged to /root/dradis-ce/extensions/x86_64-linux/2.5.0/nokogumbo-2.0.1/gem_make.out

An error occurred while installing nokogumbo (2.0.1), and Bundler cannot continue.
Make sure that `gem install nokogumbo -v '2.0.1' --source 'https://rubygems.org/'` succeeds before bundling.

In Gemfile:
  sanitize was resolved to 5.0.0, which depends on
    nokogumbo

== Command ["bundle install"] failed ==

Solution

As you can see the error is throwing while executing bundle install. So I would suggest you to update you gem by executing gem update --system

Edit:

The second error is throwing because nokogiri gem is not installed.
To install execute gem install nokogiri