$ pip freeze | grep beautifulsoup4
beautifulsoup4==4.6.3

$ python
Python 3.7.0 (default, Jul 23 2018, 20:24:19)
[Clang 9.0.0 (clang-900.0.39.2)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from bs4 import BeautifulSoup
>>> text = "<![hi world]>"
>>> BeautifulSoup(text, 'html.parser')
/Users/conradroche/solvvy/ml-pipeline/venv/lib/python3.7/site-packages/bs4/builder/_htmlparser.py:78: UserWarning: unknown status keyword 'hi ' in marked section
  warnings.warn(msg)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/conradroche/solvvy/ml-pipeline/venv/lib/python3.7/site-packages/bs4/__init__.py", line 282, in __init__
    self._feed()
  File "/Users/conradroche/solvvy/ml-pipeline/venv/lib/python3.7/site-packages/bs4/__init__.py", line 343, in _feed
    self.builder.feed(self.markup)
  File "/Users/conradroche/solvvy/ml-pipeline/venv/lib/python3.7/site-packages/bs4/builder/_htmlparser.py", line 247, in feed
    parser.feed(markup)
  File "/usr/local/Cellar/python/3.7.0/Frameworks/Python.framework/Versions/3.7/lib/python3.7/html/parser.py", line 111, in feed
    self.goahead(0)
  File "/usr/local/Cellar/python/3.7.0/Frameworks/Python.framework/Versions/3.7/lib/python3.7/html/parser.py", line 179, in goahead
    k = self.parse_html_declaration(i)
  File "/usr/local/Cellar/python/3.7.0/Frameworks/Python.framework/Versions/3.7/lib/python3.7/html/parser.py", line 264, in parse_html_declaration
    return self.parse_marked_section(i)
  File "/usr/local/Cellar/python/3.7.0/Frameworks/Python.framework/Versions/3.7/lib/python3.7/_markupbase.py", line 160, in parse_marked_section
    if not match:
UnboundLocalError: local variable 'match' referenced before assignment
>>>