test_builtin_casters.py test_string_view: Python 2 c++17, c++2a compa…

[rwgk]

…tibility.

Tested with 2.7.18rc1, built with Py_UNICODE_SIZE 4.
Change also tested with Python 3.8.

[YannickJadoul]

Same is done here:

pybind11/tests/test_builtin_casters.py

Lines 63 to 85 in a38dfee

	assert m.ord_char16(u'a') == 0x61
	assert m.ord_char16(u'é') == 0xE9
	assert m.ord_char16_lv(u'ê') == 0xEA
	assert m.ord_char16(u'Ā') == 0x100
	assert m.ord_char16(u'‽') == 0x203d
	assert m.ord_char16(u'♥') == 0x2665
	assert m.ord_char16_lv(u'♡') == 0x2661
	with pytest.raises(ValueError) as excinfo:
	assert m.ord_char16(u'🎂') == 0x1F382 # requires surrogate pair
	assert str(excinfo.value) == toobig_message(0x10000)
	with pytest.raises(ValueError) as excinfo:
	assert m.ord_char16(u'aa')
	assert str(excinfo.value) == toolong_message
	assert m.ord_char32(u'a') == 0x61
	assert m.ord_char32(u'é') == 0xE9
	assert m.ord_char32(u'Ā') == 0x100
	assert m.ord_char32(u'‽') == 0x203d
	assert m.ord_char32(u'♥') == 0x2665
	assert m.ord_char32(u'🎂') == 0x1F382
	with pytest.raises(ValueError) as excinfo:
	assert m.ord_char32(u'aa')
	assert str(excinfo.value) == toolong_message

So seems great to me! :-)

[rwgk]

Thanks a lot Yannick for pointing out the other test using the same approach, I missed that. Since there is a precedence for what I'm doing I'll merge this PR now, to get a baseline for my work on PR #2256.