Auto-correct RuboCop offenses

Output:

```
solidus_dev_support 17:27:56 $ bundle exec rubocop --auto-correct
Inspecting 29 files
........CC...C..C............

Offenses:

lib/solidus_dev_support/rake_tasks.rb:16:35: C: [Corrected] Style/FetchEnvVar: Use ENV.fetch('DUMMY_PATH', 'spec/dummy') instead of ENV['DUMMY_PATH'] || 'spec/dummy'.
      @test_app_path = @root.join(ENV['DUMMY_PATH'] || 'spec/dummy')
                                  ^^^^^^^^^^^^^^^^^
lib/solidus_dev_support/rake_tasks.rb:46:19: C: [Corrected] Style/FetchEnvVar: Use ENV.fetch('DUMMY_PATH') or ENV.fetch('DUMMY_PATH', nil) instead of ENV['DUMMY_PATH'].
        directory ENV['DUMMY_PATH'] do
                  ^^^^^^^^^^^^^^^^^
lib/solidus_dev_support/rake_tasks.rb:64:60: C: [Corrected] Style/FetchEnvVar: Use ENV.fetch('DUMMY_PATH') or ENV.fetch('DUMMY_PATH', nil) instead of ENV['DUMMY_PATH'].
        ::RSpec::Core::RakeTask.new(:specs, [] => FileList[ENV['DUMMY_PATH']]) do |t|
                                                           ^^^^^^^^^^^^^^^^^
lib/solidus_dev_support/rake_tasks.rb:85:37: C: [Corrected] Style/FetchEnvVar: Use ENV.fetch('UNRELEASED_VERSION') { gemspec.version } instead of ENV['UNRELEASED_VERSION'] || gemspec.version.
        config.future_release = "v#{ENV['UNRELEASED_VERSION'] || gemspec.version}"
                                    ^^^^^^^^^^^^^^^^^^^^^^^^^
lib/solidus_dev_support/rspec/capybara.rb:6:24: C: [Corrected] Style/RedundantParentheses: Don't use parentheses around a method call.
CAPYBARA_WINDOW_SIZE = (ENV.fetch('CAPYBARA_WINDOW_SIZE', '1920x1080')).split('x', 2).map(&:to_i)
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
lib/solidus_dev_support/rspec/capybara.rb:6:25: C: [Corrected] Style/FetchEnvVar: Use ENV.fetch('CAPYBARA_WINDOW_SIZE', '1920x1080') instead of ENV['CAPYBARA_WINDOW_SIZE'] || '1920x1080'.
CAPYBARA_WINDOW_SIZE = (ENV['CAPYBARA_WINDOW_SIZE'] || '1920x1080').split('x', 2).map(&:to_i)
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^
lib/solidus_dev_support/rspec/capybara.rb:8:30: C: [Corrected] Style/RedundantParentheses: Don't use parentheses around a method call.
Capybara.javascript_driver = (ENV.fetch('CAPYBARA_JAVASCRIPT_DRIVER', "solidus_chrome_headless")).to_sym
                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
lib/solidus_dev_support/rspec/capybara.rb:8:31: C: [Corrected] Style/FetchEnvVar: Use ENV.fetch('CAPYBARA_JAVASCRIPT_DRIVER', "solidus_chrome_headless") instead of ENV['CAPYBARA_JAVASCRIPT_DRIVER'] || "solidus_chrome_headless".
Capybara.javascript_driver = (ENV['CAPYBARA_JAVASCRIPT_DRIVER'] || "solidus_chrome_headless").to_sym
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
lib/solidus_dev_support/rspec/spec_helper.rb:17:22: C: [Corrected] Style/FetchEnvVar: Use ENV.fetch('FAIL_FAST', false) instead of ENV['FAIL_FAST'] || false.
  config.fail_fast = ENV['FAIL_FAST'] || false
                     ^^^^^^^^^^^^^^^^
lib/solidus_dev_support/templates/extension/Gemfile:17:6: C: [Corrected] Style/FetchEnvVar: Use ENV.fetch('DB') or ENV.fetch('DB', nil) instead of ENV['DB'].
case ENV['DB']
     ^^^^^^^^^

29 files inspected, 10 offenses detected, 10 offenses corrected
```

Author: gsmendoza

lib/solidus_dev_support/rake_tasks.rb

@@ -13,7 +13,7 @@ def self.install(*args)
 
     def initialize(root: Dir.pwd)
       @root = Pathname(root)
-      @test_app_path = @root.join(ENV['DUMMY_PATH'] || 'spec/dummy')
+      @test_app_path = @root.join(ENV.fetch('DUMMY_PATH', 'spec/dummy'))
       @gemspec = Bundler.load_gemspec(@root.glob("{,*}.gemspec").first)
     end
 
@@ -43,7 +43,7 @@ def install_test_app_task
           cd root
         end
 
-        directory ENV['DUMMY_PATH'] do
+        directory ENV.fetch('DUMMY_PATH', nil) do
           Rake::Task['extension:test_app'].invoke
         end
       end
@@ -61,7 +61,7 @@ def install_rspec_task
       require 'rspec/core/rake_task'
 
       namespace :extension do
-        ::RSpec::Core::RakeTask.new(:specs, [] => FileList[ENV['DUMMY_PATH']]) do |t|
+        ::RSpec::Core::RakeTask.new(:specs, [] => FileList[ENV.fetch('DUMMY_PATH', nil)]) do |t|
           # Ref: https://circleci.com/docs/2.0/configuration-reference#store_test_results
           # Ref: https://github.com/solidusio/circleci-orbs-extensions#test-results-rspec
           if ENV['TEST_RESULTS_PATH']
@@ -82,7 +82,7 @@ def install_changelog_task
 
         config.user = repo.owner
         config.project = repo.name
-        config.future_release = "v#{ENV['UNRELEASED_VERSION'] || gemspec.version}"
+        config.future_release = "v#{ENV.fetch('UNRELEASED_VERSION') { gemspec.version }}"
 
       rescue Octokit::InvalidRepository
         warn <<~WARN

lib/solidus_dev_support/rspec/capybara.rb

@@ -3,9 +3,9 @@
 require 'webdrivers/chromedriver'
 
 # Allow to override the initial windows size
-CAPYBARA_WINDOW_SIZE = (ENV['CAPYBARA_WINDOW_SIZE'] || '1920x1080').split('x', 2).map(&:to_i)
+CAPYBARA_WINDOW_SIZE = ENV.fetch('CAPYBARA_WINDOW_SIZE', '1920x1080').split('x', 2).map(&:to_i)
 
-Capybara.javascript_driver = (ENV['CAPYBARA_JAVASCRIPT_DRIVER'] || "solidus_chrome_headless").to_sym
+Capybara.javascript_driver = ENV.fetch('CAPYBARA_JAVASCRIPT_DRIVER', "solidus_chrome_headless").to_sym
 Capybara.default_max_wait_time = 10
 Capybara.server = :puma, { Silent: true } # A fix for rspec/rspec-rails#1897
 

lib/solidus_dev_support/rspec/spec_helper.rb

@@ -14,7 +14,7 @@
   config.mock_with :rspec
   config.color = true
 
-  config.fail_fast = ENV['FAIL_FAST'] || false
+  config.fail_fast = ENV.fetch('FAIL_FAST', false)
   config.order = 'random'
 
   config.raise_errors_for_deprecations!

lib/solidus_dev_support/templates/extension/Gemfile

@@ -14,7 +14,7 @@ gem 'rails', '>0.a'
 # Provides basic authentication functionality for testing parts of your engine
 gem 'solidus_auth_devise'
 
-case ENV['DB']
+case ENV.fetch('DB', nil)
 when 'mysql'
   gem 'mysql2'
 when 'postgresql'