`PyErr::api_call_failed` should return a `SystemError` when no error is set

17f94e2888/Python/ceval.c (L4330-L4333)

CHANGELOG.md

@@ -10,7 +10,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ### Changed
 
-- Change `PyErr::fetch()` to return `Option<PyErr>`. [#1728](https://github.com/PyO3/pyo3/pull/1728)
+- Change `PyErr::fetch()` to return `Option<PyErr>`. [#1717](https://github.com/PyO3/pyo3/pull/1717)
 
 ## [0.14.2] - 2021-08-09
 

src/err/mod.rs

@@ -254,9 +254,20 @@ impl PyErr {
     /// Retrieves the current error from the Python interpreter's global state.
     ///
     /// The error is cleared from the Python interpreter.
-    /// Panics if no error is set
+    /// If no error is set, returns a `SystemError` in release mode,
+    /// panics in debug mode.
     pub(crate) fn api_call_failed(py: Python) -> PyErr {
-        PyErr::fetch(py).expect("exception missing")
+        #[cfg(debug_assertions)]
+        {
+            PyErr::fetch(py).expect("error return without exception set")
+        }
+        #[cfg(not(debug_assertions))]
+        {
+            use crate::exceptions::PySystemError;
+
+            PyErr::fetch(py)
+                .unwrap_or_else(|| PySystemError::new_err("error return without exception set"))
+        }
     }
 
     /// Creates a new exception type with the given name, which must be of the form