Make .info.yml syntax errors tell you where they come from; also non-required modules shouldn't break the installer

Updated: Comment #0

Problem/Motivation

I accidentally left a contrib module with a half-converted info file in my codebase when reinstalling and got this:

What the huh?

This is before I've even selected an install profile. The error message does not give me a clue as to where it is from; it just appears Drupal is broken.

Proposed resolution

• Make the error messages presented for .info.yml (and possibly other .yml) syntax errors identify the file that contains the bug.
• Don't break the installer just because there's a dud module sitting unused on the file system.

Remaining tasks

TBD

Related Issues

#2085231: [META] Track and resolve examples of brittleness
#2057259: Malformed modulename.info.yml file causes fatal error