1 files changed, 22 insertions, 18 deletions

diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index 981ead2172..f63f06a145 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -59,15 +59,11 @@ BaseException_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 static int
 BaseException_init(PyBaseExceptionObject *self, PyObject *args, PyObject *kwds)
 {
-    PyObject *tmp;
-
     if (!_PyArg_NoKeywords(Py_TYPE(self)->tp_name, kwds))
         return -1;
 
-    tmp = self->args;
-    self->args = args;
-    Py_INCREF(self->args);
-    Py_XDECREF(tmp);
+    Py_INCREF(args);
+    Py_XSETREF(self->args, args);
 
     return 0;
 }
@@ -234,7 +230,7 @@ BaseException_set_tb(PyBaseExceptionObject *self, PyObject *tb)
         return -1;
     }
 
-    Py_XINCREF(tb);
+    Py_INCREF(tb);
     Py_XSETREF(self->traceback, tb);
     return 0;
 }
@@ -328,11 +324,10 @@ PyException_GetCause(PyObject *self) {
 
 /* Steals a reference to cause */
 void
-PyException_SetCause(PyObject *self, PyObject *cause) {
-    PyObject *old_cause = ((PyBaseExceptionObject *)self)->cause;
-    ((PyBaseExceptionObject *)self)->cause = cause;
+PyException_SetCause(PyObject *self, PyObject *cause)
+{
     ((PyBaseExceptionObject *)self)->suppress_context = 1;
-    Py_XDECREF(old_cause);
+    Py_XSETREF(((PyBaseExceptionObject *)self)->cause, cause);
 }
 
 PyObject *
@@ -344,10 +339,9 @@ PyException_GetContext(PyObject *self) {
 
 /* Steals a reference to context */
 void
-PyException_SetContext(PyObject *self, PyObject *context) {
-    PyObject *old_context = ((PyBaseExceptionObject *)self)->context;
-    ((PyBaseExceptionObject *)self)->context = context;
-    Py_XDECREF(old_context);
+PyException_SetContext(PyObject *self, PyObject *context)
+{
+    Py_XSETREF(((PyBaseExceptionObject *)self)->context, context);
 }
 
 
@@ -714,6 +708,13 @@ ComplexExtendsException(PyExc_Exception, ImportError,
                         "module.");
 
 /*
+ *    ModuleNotFoundError extends ImportError
+ */
+
+MiddlingExtendsException(PyExc_ImportError, ModuleNotFoundError, ImportError,
+                         "Module not found.");
+
+/*
  *    OSError extends Exception
  */
 
@@ -993,7 +994,7 @@ OSError_init(PyOSErrorObject *self, PyObject *args, PyObject *kwds)
     return 0;
 
 error:
-    Py_XDECREF(args);
+    Py_DECREF(args);
     return -1;
 }
 
@@ -1073,8 +1074,7 @@ OSError_str(PyOSErrorObject *self)
     }
     if (self->myerrno && self->strerror)
         return PyUnicode_FromFormat("[Errno %S] %S",
-                                    self->myerrno ? self->myerrno: Py_None,
-                                    self->strerror ? self->strerror: Py_None);
+                                    self->myerrno, self->strerror);
     return BaseException_str((PyBaseExceptionObject *)self);
 }
 
@@ -2478,6 +2478,7 @@ _PyExc_Init(PyObject *bltinmod)
     PRE_INIT(SystemExit)
     PRE_INIT(KeyboardInterrupt)
     PRE_INIT(ImportError)
+    PRE_INIT(ModuleNotFoundError)
     PRE_INIT(OSError)
     PRE_INIT(EOFError)
     PRE_INIT(RuntimeError)
@@ -2550,6 +2551,7 @@ _PyExc_Init(PyObject *bltinmod)
     POST_INIT(SystemExit)
     POST_INIT(KeyboardInterrupt)
     POST_INIT(ImportError)
+    POST_INIT(ModuleNotFoundError)
     POST_INIT(OSError)
     INIT_ALIAS(EnvironmentError, OSError)
     INIT_ALIAS(IOError, OSError)
@@ -2612,7 +2614,9 @@ _PyExc_Init(PyObject *bltinmod)
     ADD_ERRNO(BlockingIOError, EWOULDBLOCK);
     POST_INIT(BrokenPipeError);
     ADD_ERRNO(BrokenPipeError, EPIPE);
+#ifdef ESHUTDOWN
     ADD_ERRNO(BrokenPipeError, ESHUTDOWN);
+#endif
     POST_INIT(ChildProcessError);
     ADD_ERRNO(ChildProcessError, ECHILD);
     POST_INIT(ConnectionAbortedError);