Decode an error message

Explains an error or stack trace in plain words and gives the likely fixes in order.

I got this error:

```
{{FULL ERROR AND STACK TRACE}}
```

Context: {{WHAT I WAS DOING, STACK, VERSIONS}}

Relevant code:
```
{{CODE}}
```

1. Explain what the error means in plain words.
2. List the likely causes, most likely first, and how to confirm each one.
3. The fix for the most likely cause.
4. How to prevent it next time (test, type, lint rule).

If you need more information to be sure, ask for it instead of guessing.