charmcraft build failed on ubuntu focal

I am using snap for charmcraft.

Also, I added a charmcraft yaml file as prompted:

cat charmcraft.yaml

type: charm
bases:
  - name: "ubuntu"
    channel: "20.04"
    architectures: ["amd64"]

charmcraft clean && charmcraft build -t

```
    from .environment import Environment as Environment
  File "/tmp/pip-install-3z_ax2yv/Jinja2/src/jinja2/environment.py", line 15, in <module>
    from markupsafe import Markup
ModuleNotFoundError: No module named 'markupsafe'
```

Even though I modified requirements.txt to be like this:

```
cat requirements.txt

wheel
markupsafe # markupsafe is added for above error
charmhelpers
ops
```
But error is same.

full output: https://pastebin.canonical.com/p/3f43XBv7pB/