[WTF-2256]: Throw non-empty directory error using preferred mechanism

[weirdwater]

#123 reported that the generator does not throw an understandable error when the target directory is non-empty. A check for this already existed, but the mechanism used for reporting the error no longer seems to be supported by yeoman. This PR fixes the situation by throwing the error instead, which is the preferred mechanism described in the yeoman docs.

Checklist

• Contains unit tests ❌
• Contains breaking changes ❌
• Did you update version and changelog? ✅
• PR title properly formatted ([XX-000]: description)? ✅ ❌

This PR contains

• Bug fix
• Feature
• Refactor
• Documentation
• Other (describe)

What is the purpose of this PR?

To address the not understandable error reported by issue #123

Relevant changes

Used a different mechanism for raising the error. The previous method seems to have been an internal api that was not officially documented but recommended on stack overflow.

What should be covered while testing?

Try generating a widget in a directory that is not empty. I.e.:

# First check out this branch and run `npm install` inside the generator-widget package.

mkdir testWidget
touch testWidget/foo

yo /path/to/widgets-tools/packages/generator-widget/generators/app TestWidget

[LEGIO-SEXTA-FERRATA]

The title format we follow in this GitHub repository -as opposed to the AppDev repo on GitLab- has a quirk. There should be a colon (:) after the brackets pointing to the JIRA issue.

As you can also see, this is extremely minor. I would be okay if you didn't bother with it. But just wanted to mention as a reminder for future PRs.

[LEGIO-SEXTA-FERRATA]

I left a few comments. But nevertheless, approving this PR. As the issues are quite minor, it's okay if you don't want to bother.

If you want to do them, I'll re-approve later. 👍