fix: exit with an error when some config file was found but lacks on reading permissions

[micalevisk]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: closes #2434

What is the new behavior?

exit with an error. See:

demo.mp4

We got the same output for nest generate command

Does this PR introduce a breaking change?

[ ] Yes
[x] No

[kamilmysliwiec]

lgtm