Apply review comments

Author: mtsokol

include/pybind11/numpy.h

@@ -120,6 +120,26 @@ inline numpy_internals &get_numpy_internals() {
     return *ptr;
 }
 
+module_ import_numpy_core_submodule(const char * submodule_name) {
+    try {
+        return module_::import(
+            (std::string("numpy._core.") + submodule_name).c_str()
+        );
+    } catch (error_already_set &ex) {
+        if (!ex.matches(PyExc_ImportError)) throw;
+        try {
+            return module_::import(
+                (std::string("numpy.core.") + submodule_name).c_str()
+            );
+        } catch(error_already_set &ex) {
+            if (!ex.matches(PyExc_ImportError)) throw;
+            throw import_error(
+                std::string("pybind11 couldn't import ") + submodule_name + " from numpy."
+            );
+        }
+    }
+}
+
 template <typename T>
 struct same_size {
     template <typename U>
@@ -263,12 +283,7 @@ struct npy_api {
     };
 
     static npy_api lookup() {
-        module_ m;
-        try {
-            m = module_::import("numpy._core.multiarray");
-        } catch (error_already_set &) {
-            m = module_::import("numpy.core.multiarray");
-        }
+        module_ m = import_numpy_core_submodule("multiarray");
         auto c = m.attr("_ARRAY_API");
         void **api_ptr = (void **) PyCapsule_GetPointer(c.ptr(), nullptr);
         npy_api api;
@@ -631,13 +646,11 @@ class dtype : public object {
 
 private:
     static object _dtype_from_pep3118() {
-        module_ m;
-        try {
-            m = module_::import("numpy._core._internal");
-        } catch (error_already_set &) {
-            m = module_::import("numpy.core._internal");
-        }
-        static PyObject *obj = m.attr("_dtype_from_pep3118").cast<object>().release().ptr();
+        module_ m = import_numpy_core_submodule("_internal");
+        static PyObject *obj = m.attr("_dtype_from_pep3118")
+                                   .cast<object>()
+                                   .release()
+                                   .ptr();
         return reinterpret_borrow<object>(obj);
     }