Description

To maintainers, it is clear what _errex is, because we're working with
it frequently. The nameing choice, however, was (IMHO) no good. It is
needlessly short (why abbreviate error) and does not communicate its
functionality very well.

Now, it's very clear and yet not too long.## Type of change

• Improvement (non-breaking change that does improve existing functionality)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (README.md or the documentation under docs/)
• If necessary I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes