Python find_all_next в BeautifulSoup не может найти строку

Вы можете использовать регулярное выражение

import re
data = '''
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'''

r = re.compile(r'username":"(.*)(? = ","blocked)')
print(r.findall(data))

Или, для тех из нас, кто не любит регулярное выражение (подтолкнуть, подтолкнуть @QHarr: D), вы можете попробовать это:

data = [your quote above]
data_list = data.split(",")
for i in data_list:
   if 'username' in i:
       print(i)

Выход:

"username":"devils..tea."