Multiline error messages are cut off and don't appear in ALEDetail

## Information

some error messages, eg. those from `mypy` with `pretty` set to `true` are multi line, however only the top line is shown in the command line and in `ALEDetail`:



i can see the full error message in `ALEInfo`:

```
xxx.py:2:1: error: Cannot find implementation or library stub for
module named "pydantic" [import]
from pydantic import BaseModel
^
```

**VIM version**

```
NVIM v0.5.0
Build type: Release
```

Operating System: Mac OSX 10.15.7 Catalina

## What went wrong

as described above. i had a look through the docs and open issues but couldn't find much on this, is there a setting or config option i'm missing?