Arch Linux

Description:
When I try to run yaml2po I get the following error:
```
Traceback (most recent call last):
File "/usr/bin/yaml2po", line 33, in <module>
sys.exit(load_entry_point('translate-toolkit==3.4.1', 'console_scripts', 'yaml2po')())
File "/usr/bin/yaml2po", line 25, in importlib_load_entry_point
return next(matches).load()
File "/usr/lib/python3.9/importlib/metadata.py", line 77, in load
module = import_module(match.group('module'))
File "/usr/lib/python3.9/importlib/__init__.py", line 127, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 850, in exec_module
File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
File "/usr/lib/python3.9/site-packages/translate/convert/yaml2po.py", line 26, in <module>
from translate.storage import po, yaml
File "/usr/lib/python3.9/site-packages/translate/storage/yaml.py", line 24, in <module>
from ruamel.yaml import YAML, YAMLError
ModuleNotFoundError: No module named 'ruamel'
```

To fix it, I must add the package `python-ruamel-yaml`. This package should therefore be marked as a dependency.

Additional info:
* Version: 3.4.1-1

Steps to reproduce:
- Install `translate-toolkit`
- Try to use `yaml2po` to convert a .yaml file to .po