PBaseException: add missing with_traceback builtin method

Author: cosminbasca

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/exception/BaseExceptionBuiltins.java

@@ -36,6 +36,7 @@
 import com.oracle.graal.python.builtins.PythonBuiltins;
 import com.oracle.graal.python.builtins.objects.PNone;
 import com.oracle.graal.python.builtins.objects.list.PList;
+import com.oracle.graal.python.builtins.objects.traceback.PTraceback;
 import com.oracle.graal.python.builtins.objects.tuple.PTuple;
 import com.oracle.graal.python.nodes.expression.CastToListNode;
 import com.oracle.graal.python.nodes.function.PythonBuiltinNode;
@@ -156,4 +157,21 @@ public Object traceback(PBaseException self) {
             return self.getTraceback(factory());
         }
     }
+
+    @Builtin(name = "with_traceback", fixedNumOfArguments = 2)
+    @GenerateNodeFactory
+    public abstract static class WithTracebackNode extends PythonBuiltinNode {
+
+        @Specialization
+        public Object withTraceback(PBaseException self, @SuppressWarnings("unused") PNone tb) {
+            self.clearTraceback();
+            return PNone.NONE;
+        }
+
+        @Specialization
+        public Object withTraceback(PBaseException self, PTraceback tb) {
+            self.setTraceback(tb);
+            return PNone.NONE;
+        }
+    }
 }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/exception/PBaseException.java

@@ -114,6 +114,10 @@ public void setTraceback(PTraceback traceback) {
         this.traceback = traceback.getException().traceback;
     }
 
+    public void clearTraceback() {
+        this.traceback = new PTraceback[0];
+    }
+
     /**
      * Can be null in case of lazily formatted arguments.
      */