[action][ensure_env_vars] efficiency improvement

[crazymanish]

Checklist

• I've run bundle exec rspec from the root directory to see all new and existing tests pass
• I've followed the fastlane code style and run bundle exec rubocop -a to ensure the code style is valid
• I've read the Contribution Guidelines
• I've updated the documentation if necessary.

Motivation and Context

• Problem: If multiple ENV variables are missing then the user has to run ensure_env_vars multiple times because it always EXIT after found the first missing ENV variable.
• This is slightly inconvenience because Fastlane uses lots of ENV variables and good to report all expected missing ENV variables after one run itself to save time and to avoid Fastlane run ensure_env_vars multiple times 😇

Description

• Made ensure_env_vars more efficient, now it will report all missing ENV variables after one run itself.
• Please see the screenshot for more details

Testing Steps

• Update Gemfile and run bundle install with

gem "fastlane", :git => "git@github.com:crazymanish/fastlane.git", :branch => "ensure-env-vars-improvement"

• With the below test lane, run bundle exec fastlane test

lane :test do
    #ENV["GITHUB_API_TOKEN_MISSING_EXAMPLE"] = 'xxxxx-xxxxxxx-xxxxxxx'
    ENV["GYM_SCHEME"] = "MyApp"
    ENV["GYM_EXPORT_METHOD"] = 'app-store'
    #ENV["GYM_CLEAN"] = 'true'
    ENV["GYM_SILENT"] = 'true'
    #ENV["SLACK_API_TOKEN_MISSING_EXAMPLE"] = 'xxxxx-xxxxxxx-xxxxxxx'

    ensure_env_vars(
      env_vars: [
        'GITHUB_API_TOKEN_MISSING_EXAMPLE',
        'GYM_SCHEME',
        'GYM_EXPORT_METHOD',
        'GYM_CLEAN',
        'GYM_SILENT',
        'SLACK_API_TOKEN_MISSING_EXAMPLE'
      ]
    )
  end

Screenshot

[ainame]

Suggested change

	is_one = missing_variables.length == 1
	UI.user_error!("Missing environment variable#{is_one ? '' : 's'} '#{missing_variables.join('\', \'')}'") unless missing_variables.empty?
	UI.user_error!("Missing environment variable(s) '#{missing_variables.join('\', \'')}'") unless missing_variables.empty?

I understand that this logic comes from the below line but isn't this enough here? 🙂 (and reusing the same local variable for a different purpose doesn't sound good in general).

[ainame]

🚀

[joshdholtz]

This is 🔥 Thanks for fixing this! Really appreciate all of your contributions ❤️

[fastlane-bot]

Hey @crazymanish 👋

Thank you for your contribution to fastlane and congrats on getting this pull request merged 🎉
The code change now lives in the master branch, however it wasn't released to RubyGems yet.
We usually ship about once a week, and your PR will be included in the next one.

Please let us know if this change requires an immediate release by adding a comment here 👍
We'll notify you once we shipped a new release with your changes 🚀

[fastlane-bot]

Congratulations! 🎉 This was released as part of fastlane 2.181.0 🚀