Use error bullets for `nonexistent`, `ambiguous`, and `invalid` errors

From Hadley:

maybe:
```
Error: Nonexistent time due to daylight saving time at location 1. Resolve nonexistent time issues by specifying the `nonexistent` argument.
```
should be
```
Error: Nonexistent time due to daylight saving time at location 1. 
i Resolve nonexistent time issues by specifying the `nonexistent` argument.
```