Add error_fetch_and_normalize::release_py_object_references() and use from error_already_set dtor.

Author: rwgk

include/pybind11/pybind11.h

@@ -2626,15 +2626,12 @@ void print(Args &&...args) {
 }
 
 inline error_already_set::~error_already_set() {
-    auto e = m_fetched_error;
-    if (!(e.m_type || e.m_value || e.m_trace)) {
+    if (!m_fetched_error.has_py_object_references()) {
         return; // Avoid gil and scope overhead if there is nothing to release.
     }
     gil_scoped_acquire gil;
     error_scope scope;
-    e.m_type.release().dec_ref();
-    e.m_value.release().dec_ref();
-    e.m_trace.release().dec_ref();
+    m_fetched_error.release_py_object_references();
 }
 
 inline error_already_set::error_already_set(const error_already_set &other)

include/pybind11/pytypes.h

@@ -531,6 +531,14 @@ struct error_fetch_and_normalize {
         return (PyErr_GivenExceptionMatches(m_type.ptr(), exc.ptr()) != 0);
     }
 
+    bool has_py_object_references() const { return m_type || m_value || m_trace; }
+
+    void release_py_object_references() {
+        m_type.release().dec_ref();
+        m_value.release().dec_ref();
+        m_trace.release().dec_ref();
+    }
+
     object m_type, m_value, m_trace;
     mutable std::string m_lazy_error_string;
     mutable bool m_lazy_error_string_completed = false;