support for walrus operator

The walrus operator which was added in Python 3.8 (:=) is not supported:
>>> import redbaron
>>> redbaron.RedBaron('''
... if foo := True:
...     print(foo)
... ''')
Traceback (most recent call last):
  File "~/.asdf/installs/python/3.10.7/lib/python3.10/site-packages/baron/baron.py", line 20, in _parse
    return parser(tokens)
  File "~/.asdf/installs/python/3.10.7/lib/python3.10/site-packages/baron/grammator.py", line 836, in parse
    return parser.parse(iter(tokens))
  File "~/.asdf/installs/python/3.10.7/lib/python3.10/site-packages/baron/parser.py", line 165, in parse
    raise ParsingError(debug_output)
baron.parser.ParsingError: Error, got an unexpected token EQUAL here:

   1
   2 if foo := <---- here

The token EQUAL should be one of those: ASSERT, BACKQUOTE, BINARY, BINARY_RAW_STRING, BINARY_STRING, BREAK, COMMENT, COMPLEX, CONTINUE, DEL, ELLIPSIS, ENDL, EXEC, FLOAT, FLOAT_EXPONANT, FLOAT_EXPONANT_COMPLEX, FROM, GLOBAL, HEXA, IMPORT, INT, INTERPOLATED_RAW_STRING, INTERPOLATED_STRING, LAMBDA, LEFT_BRACKET, LEFT_PARENTHESIS, LEFT_SQUARE_BRACKET, LONG, MINUS, NAME, NONLOCAL, NOT, OCTA, PASS, PLUS, PRINT, RAISE, RAW_STRING, RETURN, STAR, STRING, TILDE, UNICODE_RAW_STRING, UNICODE_STRING, YIELD

Baron has failed to parse this input. If this is valid python code (and by that I mean that the python binary successfully parse this code without any syntax error) (also consider that baron does not yet parse python 3 code integrally) it would be kind if you can extract a snippet of your code that make Baron fails and open a bug here: https://github.com/PyCQA/baron/issues

Sorry for the inconvenience.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "~/.asdf/installs/python/3.10.7/lib/python3.10/site-packages/redbaron/redbaron.py", line 36, in __init__
    self.node_list = base_nodes.NodeList.from_fst(baron.parse(source_code), parent=self, on_attribute="root")
  File "~/.asdf/installs/python/3.10.7/lib/python3.10/site-packages/baron/baron.py", line 66, in parse
    return _parse(tokens, print_function)
  File "~/.asdf/installs/python/3.10.7/lib/python3.10/site-packages/baron/baron.py", line 24, in _parse
    return parser(tokens)
  File "~/.asdf/installs/python/3.10.7/lib/python3.10/site-packages/baron/grammator.py", line 836, in parse
    return parser.parse(iter(tokens))
  File "~/.asdf/installs/python/3.10.7/lib/python3.10/site-packages/baron/parser.py", line 165, in parse
    raise ParsingError(debug_output)
baron.parser.ParsingError: Error, got an unexpected token EQUAL here:

   1
   2 if foo := <---- here

The token EQUAL should be one of those: ASSERT, BACKQUOTE, BINARY, BINARY_RAW_STRING, BINARY_STRING, BREAK, COMMENT, COMPLEX, CONTINUE, DEL, ELLIPSIS, ENDL, FLOAT, FLOAT_EXPONANT, FLOAT_EXPONANT_COMPLEX, FROM, GLOBAL, HEXA, IMPORT, INT, INTERPOLATED_RAW_STRING, INTERPOLATED_STRING, LAMBDA, LEFT_BRACKET, LEFT_PARENTHESIS, LEFT_SQUARE_BRACKET, LONG, MINUS, NAME, NONLOCAL, NOT, OCTA, PASS, PLUS, RAISE, RAW_STRING, RETURN, STAR, STRING, TILDE, UNICODE_RAW_STRING, UNICODE_STRING, YIELD

Baron has failed to parse this input. If this is valid python code (and by that I mean that the python binary successfully parse this code without any syntax error) (also consider that baron does not yet parse python 3 code integrally) it would be kind if you can extract a snippet of your code that make Baron fails and open a bug here: https://github.com/PyCQA/baron/issues

Sorry for the inconvenience.
PyCQA / redbaron

support for walrus operator #216
