This line (which contains a non-ASCII digit):

    python3.9 -c "import datetime; datetime.date.fromisoformat('1963-06-1৪')"

raises:

    Traceback (most recent call last):
      File "<string>", line 1, in <module>
    ValueError: Invalid isoformat string: '1963-06-1৪'

under the C implementation of the datetime module, but when the pure Python implementation is the one imported, succeeds (and produces `datetime.date(1963, 6, 14)`)

The pure Python implementation should instead explicitly check and raise when encountering a non-ASCII string.

(On PyPy, which always uses the pure-Python implementation, this contributes to a behavioral difference)