3 files changed, 69 insertions, 1 deletions
diff --git a/Python/crossinterp.c b/Python/crossinterp.c
index f74fee3..a31b5ef 100644
--- a/Python/crossinterp.c
+++ b/Python/crossinterp.c
@@ -12,6 +12,53 @@
 #include "pycore_weakref.h"       // _PyWeakref_GET_REF()
 
 
+/**************/
+/* exceptions */
+/**************/
+
+/* InterpreterError extends Exception */
+
+static PyTypeObject _PyExc_InterpreterError = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    .tp_name = "InterpreterError",
+    .tp_doc = PyDoc_STR("An interpreter was not found."),
+    //.tp_base = (PyTypeObject *)PyExc_BaseException,
+};
+PyObject *PyExc_InterpreterError = (PyObject *)&_PyExc_InterpreterError;
+
+/* InterpreterNotFoundError extends InterpreterError */
+
+static PyTypeObject _PyExc_InterpreterNotFoundError = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    .tp_name = "InterpreterNotFoundError",
+    .tp_doc = PyDoc_STR("An interpreter was not found."),
+    .tp_base = &_PyExc_InterpreterError,
+};
+PyObject *PyExc_InterpreterNotFoundError = (PyObject *)&_PyExc_InterpreterNotFoundError;
+
+/* lifecycle */
+
+static int
+init_exceptions(PyInterpreterState *interp)
+{
+    _PyExc_InterpreterError.tp_base = (PyTypeObject *)PyExc_BaseException;
+    if (_PyStaticType_InitBuiltin(interp, &_PyExc_InterpreterError) < 0) {
+        return -1;
+    }
+    if (_PyStaticType_InitBuiltin(interp, &_PyExc_InterpreterNotFoundError) < 0) {
+        return -1;
+    }
+    return 0;
+}
+
+static void
+fini_exceptions(PyInterpreterState *interp)
+{
+    _PyStaticType_Dealloc(interp, &_PyExc_InterpreterNotFoundError);
+    _PyStaticType_Dealloc(interp, &_PyExc_InterpreterError);
+}
+
+
 /***************************/
 /* cross-interpreter calls */
 /***************************/
@@ -2099,3 +2146,18 @@ _PyXI_Fini(PyInterpreterState *interp)
         _xidregistry_fini(_get_global_xidregistry(interp->runtime));
     }
 }
+
+PyStatus
+_PyXI_InitTypes(PyInterpreterState *interp)
+{
+    if (init_exceptions(interp) < 0) {
+        return _PyStatus_ERR("failed to initialize an exception type");
+    }
+    return _PyStatus_OK();
+}
+
+void
+_PyXI_FiniTypes(PyInterpreterState *interp)
+{
+    fini_exceptions(interp);
+}
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index 45a119f..b5c7dc5 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -734,6 +734,11 @@ pycore_init_types(PyInterpreterState *interp)
         return status;
     }
 
+    status = _PyXI_InitTypes(interp);
+    if (_PyStatus_EXCEPTION(status)) {
+        return status;
+    }
+
     return _PyStatus_OK();
 }
 
@@ -1742,6 +1747,7 @@ finalize_interp_types(PyInterpreterState *interp)
 {
     _PyUnicode_FiniTypes(interp);
     _PySys_FiniTypes(interp);
+    _PyXI_FiniTypes(interp);
     _PyExc_Fini(interp);
     _PyAsyncGen_Fini(interp);
     _PyContext_Fini(interp);
diff --git a/Python/pystate.c b/Python/pystate.c
index 1a7c0c9..f0c5259 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -1216,7 +1216,7 @@ _PyInterpreterState_LookUpID(int64_t requested_id)
         HEAD_UNLOCK(runtime);
     }
     if (interp == NULL && !PyErr_Occurred()) {
-        PyErr_Format(PyExc_RuntimeError,
+        PyErr_Format(PyExc_InterpreterNotFoundError,
                      "unrecognized interpreter ID %lld", requested_id);
     }
     return interp;