Description:
community/bpython should depend on extra/python-pyxdg

Running it without it causes the following errors:

Traceback (most recent call last):
File "/usr/bin/bpython", line 33, in <module>
sys.exit(load_entry_point('bpython==0.21', 'console_scripts', 'bpython')())
File "/usr/bin/bpython", 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/bpython/curtsies.py", line 10, in <module>
from .curtsiesfrontend.repl import BaseRepl
File "/usr/lib/python3.9/site-packages/bpython/curtsiesfrontend/repl.py", line 34, in <module>
from bpython.repl import (
File "/usr/lib/python3.9/site-packages/bpython/repl.py", line 45, in <module>
from .config import getpreferredencoding
File "/usr/lib/python3.9/site-packages/bpython/config.py", line 31, in <module>
from xdg import BaseDirectory
ModuleNotFoundError: No module named 'xdg'

with the bpython-0.21-1

Steps to reproduce:
1. Remove python-pyxdg, if it is already installed.
2. Install bpython.
3. Try to run bpython.