Add back test_potentially_slicing_shared_ptr_not_convertible_error(), it got lost accidentally in commit 56d23dc

Author: rwgk

tests/test_potentially_slicing_shared_ptr.py

@@ -112,3 +112,18 @@ def test_with_wp_owner(holder_kind, set_meth, expected_code):
     gc.collect()
     if GC_IS_RELIABLE:
         assert wpo.get_code() == -999
+
+
+def test_potentially_slicing_shared_ptr_not_convertible_error():
+    with pytest.raises(Exception) as excinfo:
+        m.SH_rtrn_potentially_slicing_shared_ptr("")
+    assert str(excinfo.value) == (
+        '"str" object is not convertible to std::shared_ptr<T>'
+        " (with T = pybind11_tests::potentially_slicing_shared_ptr::VirtBase<0>)"
+    )
+    with pytest.raises(Exception) as excinfo:
+        m.SP_rtrn_potentially_slicing_shared_ptr([])
+    assert str(excinfo.value) == (
+        '"list" object is not convertible to std::shared_ptr<T>'
+        " (with T = pybind11_tests::potentially_slicing_shared_ptr::VirtBase<1>)"
+    )