Ignore some tests in Python <3.8

Author: YannickJadoul

include/pybind11/cast.h

@@ -1027,7 +1027,7 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
                 return false;
         } else if (PyFloat_Check(src.ptr())) {
             return false;
-        } else if (!convert && !PYBIND11_LONG_CHECK(src.ptr()) && !PyIndex_Check(src.ptr())) {
+        } else if (!convert && !PyIndex_Check(src.ptr()) && !PYBIND11_LONG_CHECK(src.ptr())) {
             return false;
         } else if (std::is_unsigned<py_type>::value) {
             py_value = as_unsigned<py_type>(src.ptr());

tests/test_builtin_casters.py

@@ -289,8 +289,8 @@ def cant_convert(v):
     require_implicit(DeepThought())
     cant_convert(ShallowThought())
     cant_convert(FuzzyThought())
-    if not env.PY2:
-        # I have no clue why __index__ is not picked up by Python 2's PyIndex_check
+    if env.PY >= (3, 8):
+        # Before Python 3.8, `int(obj)` does not pick up on `obj.__index__`
         assert convert(IndexedThought()) == 42
         assert noconvert(IndexedThought()) == 42
         cant_convert(RaisingThought())  # no fall-back to `__int__`if `__index__` raises