Comment 1 for bug 1960384

xav's patch is merged into master. main changes:

1. add charmcraft.yaml with `python3-marksafe`:

```
> $ cat charmcraft.yaml
type: charm
parts:
  charm:
    build-packages: [python3-markupsafe, bash]
```

2. limit Jinjia2 version:

```
cat requirements.txt
Jinja2<3
```

I have verified `charmcraft build` is working on my machine (focal).