Generated Python client is missing some imports

When I generated Pyhon client using https://editor.swagger.io/ in the file api_client.py I get this block (line 52 started):

NATIVE_TYPES_MAPPING = {
        'int': int,
        'long': int if six.PY3 else long,  # noqa: F821
        'float': float,
        'str': str,
        'bool': bool,
        'date': datetime.date,
        'datetime': datetime.datetime,
        'object': object,
    }

But under Python 3.6.5 long is not supported anymore and only int is available with long integrated behavior.

Start with the generated api_client.py around line 52 and trace which swagger-codegen template produces this block. Reproduce generation through editor.swagger.io with Python 3.6.5, then verify the generated client no longer references an unavailable Python 3 long type.