问题可能是由于BeautifulSoup默认只使用ASCII字符集解析XML导致的。可以尝试使用lxml XML解析器来解决，它支持处理更广泛的字符集，包括UTF-8、ISO-8859-1等。

示例代码：

from bs4 import BeautifulSoup
import requests

# 使用lxml解析器
response = requests.get(url)
soup = BeautifulSoup(response.text, 'lxml')

另一种解决方法是修改BeautifulSoup的默认解析器，例如：

from bs4 import BeautifulSoup
import requests
from bs4.dammit import EntitySubstitution

# 自定义解析器
class MyBeautifulSoup(BeautifulSoup):
    def __init__(self, markup="", features=None, builder=None,
                 parse_only=None, from_encoding=None, exclude_encodings=None,
                 **kwargs):
        if exclude_encodings is None:
            exclude_encodings = [
                'latin1',
            ]
        else:
            exclude_encodings.append('latin1')
        super().__init__(markup, features, builder, parse_only, from_encoding,
                         exclude_encodings,
                         **kwargs)

# 使用自定义解析器
response = requests.get(url)
soup = MyBeautifulSoup(response.text, 'xml')