Simplify code per review suggestion

Delegate newly created Python object memory management
to a unique_ptr to ensure it gets properly handled in case
an exception is thrown.

Check for possible exception in flight, and handle it correctly.

Author: oleksandr-pavlyk

dpctl/apis/include/dpctl4pybind11.hpp

@@ -769,44 +769,32 @@ class usm_memory : public py::object
         // create memory object owned by mock_owner, it is a new reference
         PyObject *_memory =
             api.Memory_Make_(usm_ref, nbytes, QRef, mock_owner.ptr());
+        auto ref_count_decrementer = [](PyObject *o) noexcept { Py_DECREF(o); };
 
-        bool is_ok =
-            (PyObject_TypeCheck(
-                 _memory, ::dpctl::detail::dpctl_capi::get().Py_MemoryType_) !=
-             0);
-
-        if (is_ok) {
-            std::shared_ptr<void> *opaque_ptr = nullptr;
-            std::exception_ptr eptr;
-            try {
-                opaque_ptr = new std::shared_ptr<void>(shptr);
-            } catch (const std::exception &e) {
-                eptr = std::make_exception_ptr(e);
-            }
-            if (eptr) {
-                Py_DECREF(_memory);
-                std::rethrow_exception(eptr);
-            }
-            Py_MemoryObject *memobj =
-                reinterpret_cast<Py_MemoryObject *>(_memory);
-            // replace mock_owner capsule as the owner
-            memobj->refobj = Py_None;
-            // set opaque ptr field, usm_memory now knowns that USM is managed
-            // by smart pointer
-            memobj->_opaque_ptr = reinterpret_cast<void *>(opaque_ptr);
-
-            // _memory will delete created copies of sycl::queue, and
-            // std::shared_ptr and the deleter of the shared_ptr<void> is
-            // supposed to free the USM allocation
-            m_ptr = _memory;
-            q_uptr.release();
-        }
-        else {
-            Py_DECREF(_memory);
+        using py_uptrT =
+            std::unique_ptr<PyObject, decltype(ref_count_decrementer)>;
+        auto memory_uptr = py_uptrT(_memory, ref_count_decrementer);
 
-            throw std::runtime_error(
-                "Internal error: _Memory object created did not pass check");
+        if (!_memory) {
+            throw py::error_already_set();
         }
+
+        std::shared_ptr<void> *opaque_ptr = nullptr;
+        opaque_ptr = new std::shared_ptr<void>(shptr);
+
+        Py_MemoryObject *memobj = reinterpret_cast<Py_MemoryObject *>(_memory);
+        // replace mock_owner capsule as the owner
+        memobj->refobj = Py_None;
+        // set opaque ptr field, usm_memory now knowns that USM is managed
+        // by smart pointer
+        memobj->_opaque_ptr = reinterpret_cast<void *>(opaque_ptr);
+
+        // _memory will delete created copies of sycl::queue, and
+        // std::shared_ptr and the deleter of the shared_ptr<void> is
+        // supposed to free the USM allocation
+        m_ptr = _memory;
+        q_uptr.release();
+        memory_uptr.release();
     }
 
     sycl::queue get_queue() const