Stack trace shows different exception type than print

[scidam]

There are two version of make_scanner in json module, c_make_scanner and py_make_scanner. We need to force Python to use Python version (py_make_scanner).
The following isn't to be an elegant solution, but it straightforward and clear:

import json
from json.decoder import PosInf, _CONSTANTS
from json.scanner import NUMBER_RE

_CONSTANTS.update({'+Infinity': PosInf})  # Update known constants 

def py_make_scanner(context):  # there are c-version, we need to force python to use version only
    parse_object = context.parse_object
    parse_array = context.parse_array
    parse_string = context.parse_string
    match_number = NUMBER_RE.match
    strict = context.strict
    parse_float = context.parse_float
    parse_int = context.parse_int
    parse_constant = context.parse_constant
    object_hook = context.object_hook
    object_pairs_hook = context.object_pairs_hook
    memo = context.memo

    def _scan_once(string, idx):
        try:
            nextchar = string[idx]
        except IndexError:
            raise StopIteration(idx) from None

        if nextchar == '"':
            return parse_string(string, idx + 1, strict)
        elif nextchar == '{':
            return parse_object((string, idx + 1), strict,
                _scan_once, object_hook, object_pairs_hook, memo)
        elif nextchar == '[':
            return parse_array((string, idx + 1), _scan_once)
        elif nextchar == 'n' and string[idx:idx + 4] == 'null':
            return None, idx + 4
        elif nextchar == 't' and string[idx:idx + 4] == 'true':
            return True, idx + 4
        elif nextchar == 'f' and string[idx:idx + 5] == 'false':
            return False, idx + 5

        m = match_number(string, idx)
        if m is not None:
            integer, frac, exp = m.groups()
            if frac or exp:
                res = parse_float(integer + (frac or '') + (exp or ''))
            else:
                res = parse_int(integer)
            return res, m.end()
        elif nextchar == 'N' and string[idx:idx + 3] == 'NaN':
            return parse_constant('NaN'), idx + 3
        elif nextchar == 'I' and string[idx:idx + 8] == 'Infinity':
            return parse_constant('Infinity'), idx + 8
        elif nextchar == '-' and string[idx:idx + 9] == '-Infinity':
            return parse_constant('-Infinity'), idx + 9
        elif nextchar == '+' and string[idx:idx + 9] == '+Infinity':  #  These lines were added;
            return parse_constant('+Infinity'), idx + 9
        else:
            raise StopIteration(idx)

    def scan_once(string, idx):
        try:
            return _scan_once(string, idx)
        finally:
            memo.clear()

    return scan_once

 
class PositiveInfinityJSONDecoder(json.JSONDecoder):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.scan_once = py_make_scanner(self)  # Force to use python (not c) version of py_make_scnner
 

print(json.loads('+Infinity', cls=PositiveInfinityJSONDecoder))