PythonでYouTube のアーカイブからチャットが取得できなくなった

前提・実現したいこと

PythonでYoutubeのアーカイブからチャットを取得したいです。

先月までは取得できていたのですが、今回やってみたところ取得したデータが空になってしまいました

発生している問題・エラーメッセージ

SyntaxError
invalid syntax (<unknown>, line 1)

cmdでpyファイル実行後に上記エラーがでて、jsonファイルに何も表示されていません

該当のソースコード

#!/usr/bin/env python3

from bs4 import BeautifulSoup
import ast
import requests
import requests_html
import re
import sys

# Produce a valid filename (from Django text utils).
def get_valid_filename(s):
    s = str(s).strip().replace(' ', '_')
    return re.sub(r'(?u)[^-\w.]', '', s)


# Set up variables for requests.
#target_url = sys.argv[1]
target_url = "https://www.youtube.com/watch?v=xxxx" #←コメントを取得したい番組のURL
dict_str = ''
next_url = ''
comment_data = []
#session = requests.Session()
session = requests_html.HTMLSession()
headers = {'user-agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.116 Safari/537.36'}

# Get the video page.
#html = session.get(target_url)
resp = session.get(target_url)
resp.html.render(sleep=3) 
#soup = BeautifulSoup(html.text, 'html.parser')

# Retrieve the title and sanitize so it is a valid filename.
#title = soup.find_all('title')
title = resp.html.find('title')
title = title[0].text.replace(' - YouTube', '')
title = get_valid_filename(title)

# Regex match for emoji.
RE_EMOJI = re.compile('[\U00010000-\U0010ffff]', flags=re.UNICODE)

# Find any live_chat_replay elements, get URL for next live chat message.
#for iframe in soup.find_all("iframe"):
#    if("live_chat_replay" in iframe["src"]):
#        next_url = iframe["src"]
for iframe in resp.html.find("iframe"):
    if "live_chat_replay" in iframe.attrs["src"]:
        next_url = "".join(["https://www.youtube.com", iframe.attrs["src"]])


if not next_url:
    print("Couldn't find live_chat_replay iframe. Maybe try running again?")
    sys.exit(0)

# TODO - We should fail fast if next_url is empty, otherwise you get error:
# Invalid URL '': No schema supplied. Perhaps you meant http://?

# TODO - This loop is fragile. It loops endlessly when some exceptions are hit.
while(1):

    try:
        html = session.get(next_url, headers=headers)
        soup = BeautifulSoup(html.text, 'lxml')

        # Loop through all script tags.
        for script in soup.find_all('script'):
            script_text = str(script)
            if 'ytInitialData' in script_text:
                dict_str = ''.join(script_text.split(" = ")[1:])

        # Capitalize booleans so JSON is valid Python dict.
        dict_str = dict_str.replace("false", "False")
        dict_str = dict_str.replace("true", "True")

        # Strip extra HTML from JSON.
        dict_str = re.sub(r'};.*\n.+</script>', '}', dict_str)

        # Correct some characters.
        dict_str = dict_str.rstrip("  \n;")

        # TODO: I don't seem to have any issues with emoji in the messages.
        # dict_str = RE_EMOJI.sub(r'', dict_str)

        # Evaluate the cleaned up JSON into a python dict.
        dics = ast.literal_eval(dict_str)

        # TODO: On the last pass this returns KeyError since there are no more
        # continuations or actions. Should probably just break in that case.
        continue_url = dics["continuationContents"]["liveChatContinuation"]["continuations"][0]["liveChatReplayContinuationData"]["continuation"]
        print('Found another live chat continuation:')
        print(continue_url)
        next_url = "https://www.youtube.com/live_chat_replay?continuation=" + continue_url

        # Extract the data for each live chat comment.
        for samp in dics["continuationContents"]["liveChatContinuation"]["actions"]:
            comment_data.append(str(samp) + "\n")

    # next_urlが入手できなくなったら終わり
    except requests.ConnectionError:
        print("Connection Error")
        continue
    except requests.HTTPError:
        print("HTTPError")
        break
    except requests.Timeout:
        print("Timeout")
        continue
    except requests.exceptions.RequestException as e:
        print(e)
        break
    except KeyError as e:
        error = str(e)
        if 'liveChatReplayContinuationData' in error:
            print('Hit last live chat segment, finishing job.')
        else:
            print("KeyError")
            print(e)
        break
    except SyntaxError as e:
        print("SyntaxError")
        print(e)
        break
        # continue #TODO
    except KeyboardInterrupt:
        break
    except Exception:
        print("Unexpected error:" + str(sys.exc_info()[0]))

# Write the comment data to a file named after the title of the video.
with open(title + ".json", mode='w', encoding="utf-8") as f:
    f.writelines(comment_data)

print('Comment data saved to ' + title + '.json')

試したこと

ここに問題に対して試したことを記載してください。

補足情報（FW/ツールのバージョンなど）

appdirs==1.4.4
beautifulsoup4==4.9.3
bs4==0.0.1
certifi==2020.12.5
chainmap==1.0.3
chardet==4.0.0
combomethod==1.0.12
cssselect==1.1.0
fake-useragent==0.1.11
idna==2.10
lxml==4.6.2
nulltype==2.3.1
options==1.4.10
parse==1.19.0
pyee==8.1.0
pyppeteer==0.2.5
pyquery==1.4.3
requests==2.25.1
requests-html==0.10.0
selenium==3.141.0
six==1.12.0
soupsieve==2.2
tqdm==4.56.2
urllib3==1.26.3
w3lib==1.22.0
websockets==8.1