def format_exception_only(etype, value):

    # An instance should not have a meaningful value parameter, but
    # sometimes does, particularly for string exceptions, such as
    # >>> raise string1, string2  # deprecated
    #
    # Clear these out first because issubtype(string1, SyntaxError)
    # would throw another exception and mask the original problem.
    if (isinstance(etype, BaseException) or
        isinstance(etype, types.InstanceType) or
        etype is None or type(etype) is str):
        return [_format_final_exc_line(etype, value)]

    stype = etype.__name__

    if not issubclass(etype, SyntaxError):
        return [_format_final_exc_line(stype, value)]

    # It was a syntax error; show exactly where the problem was found.
    lines = []
    try:
        msg, (filename, lineno, offset, badline) = value.args
    except Exception:
        pass
    else:
        filename = filename or "<string>"
        lines.append('  File "%s", line %d\n' % (filename, lineno))
        if badline is not None:
            if isinstance(badline, bytes):  # python 2 only
                badline = badline.decode('utf-8', 'replace')
            lines.append(u'    %s\n' % badline.strip())
            if offset is not None:
                caretspace = badline.rstrip('\n')[:offset].lstrip()
                # non-space whitespace (likes tabs) must be kept for alignment
                caretspace = ((c.isspace() and c or ' ') for c in caretspace)
                # only three spaces to account for offset1 == pos 0
                lines.append('   %s^\n' % ''.join(caretspace))
        value = msg

    lines.append(_format_final_exc_line(stype, value))
    return lines
Format the exception part of a traceback.
dataset/ETHPy150Open pytest-dev/pytest/_pytest/_code/_py2traceback.py/format_exception_only