RSSFeedLoaderで、「exception: newspaper package not found, please install it with `pip install newspaper3k`」が消えない

LangchainのRSSFeedLoaderで、RSSからドキュメントロード時に以下のエラーが発生した

ソース(rss/test.py)

from langchain_community.document_loaders import RSSFeedLoader
from langchain.indexes import VectorstoreIndexCreator
from langchain.text_splitter import CharacterTextSplitter
from langchain_openai import OpenAIEmbeddings
from langchain_community.vectorstores.inmemory import InMemoryVectorStore

urls = ["https://rss.itmedia.co.jp/rss/2.0/aiplus.xml"]

loader = RSSFeedLoader(urls=urls)

text_splitter = CharacterTextSplitter(
    separator = "\n",
    chunk_size = 400,
    chunk_overlap = 0,
    length_function = len,
)

index = VectorstoreIndexCreator(
    vectorstore_cls=InMemoryVectorStore,
    embedding=OpenAIEmbeddings(),
    text_splitter=text_splitter,
).from_loaders([loader])

エラーメッセージ

Error processing entry https://www.itmedia.co.jp/business/articles/2406/25/news053.html, exception: newspaper package not found, please install it with `pip install newspaper3k`

newspaper3kをインストールした後でも、同じエラーがでる。

% pip install newspaper3k
% python rss/test.py
Error processing entry https://www.itmedia.co.jp/news/articles/2406/25/news101.html, exception: newspaper package not found, please install it with `pip install newspaper3k`

lxml[html_clean]をインストールすることでエラーが解消した

lxml[html_clean]インストール

% pip install "lxml[html_clean]" 

エラー解消

% python rss/test.py            
Created a chunk of size 850, which is longer than the specified 400
Created a chunk of size 593, which is longer than the specified 400