Unclear error when frontmatter contains invalid colon

[pedzed]

Take the following file colon_correct.md:

---
title: "Assignment 1: Some Title"
---

# Hello world!

And take the following file colon_mistake.md:

---
title: Assignment 1: Some Title
---

# Hello world!

The latter is understandably wrong (which took me longer to realize than necessary), thus it should fail with a clear error message. It rather gives a cryptic traceback such as:

Traceback (most recent call last):
  File "PROJ_DIR/main.py", line 40, in main
    post = frontmatter.load(md_file)
  File "PROJ_DIR/.venv/lib/python3.14/site-packages/frontmatter/__init__.py", line 165, in load
    return loads(text, encoding, handler, **defaults)
  File "PROJ_DIR/.venv/lib/python3.14/site-packages/frontmatter/__init__.py", line 185, in loads
    metadata, content = parse(text, encoding, handler, **defaults)
                        ~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "PROJ_DIR/.venv/lib/python3.14/site-packages/frontmatter/__init__.py", line 92, in parse
    fm_data = handler.load(fm)