Add missing object.__subclasshook__

Fixes #165

Author: msimacek

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/object/ObjectBuiltins.java

@@ -47,6 +47,7 @@
 import static com.oracle.graal.python.nodes.SpecialMethodNames.__SETATTR__;
 import static com.oracle.graal.python.nodes.SpecialMethodNames.__SET__;
 import static com.oracle.graal.python.nodes.SpecialMethodNames.__STR__;
+import static com.oracle.graal.python.nodes.SpecialMethodNames.__SUBCLASSHOOK__;
 import static com.oracle.graal.python.runtime.exception.PythonErrorType.AttributeError;
 import static com.oracle.graal.python.runtime.exception.PythonErrorType.TypeError;
 
@@ -63,16 +64,16 @@
 import com.oracle.graal.python.builtins.objects.PNone;
 import com.oracle.graal.python.builtins.objects.PNotImplemented;
 import com.oracle.graal.python.builtins.objects.PythonAbstractObject;
-import com.oracle.graal.python.builtins.objects.cext.capi.CExtNodes;
 import com.oracle.graal.python.builtins.objects.cext.PythonAbstractNativeObject;
+import com.oracle.graal.python.builtins.objects.cext.capi.CExtNodes;
 import com.oracle.graal.python.builtins.objects.dict.PDict;
 import com.oracle.graal.python.builtins.objects.function.PBuiltinFunction;
 import com.oracle.graal.python.builtins.objects.function.PKeyword;
-import com.oracle.graal.python.builtins.objects.object.ObjectBuiltinsClinicProviders.FormatNodeClinicProviderGen;
 import com.oracle.graal.python.builtins.objects.getsetdescriptor.DescriptorDeleteMarker;
 import com.oracle.graal.python.builtins.objects.getsetdescriptor.GetSetDescriptorTypeBuiltins.DescrDeleteNode;
 import com.oracle.graal.python.builtins.objects.getsetdescriptor.GetSetDescriptorTypeBuiltins.DescrGetNode;
 import com.oracle.graal.python.builtins.objects.getsetdescriptor.GetSetDescriptorTypeBuiltins.DescrSetNode;
+import com.oracle.graal.python.builtins.objects.object.ObjectBuiltinsClinicProviders.FormatNodeClinicProviderGen;
 import com.oracle.graal.python.builtins.objects.object.ObjectBuiltinsFactory.GetAttributeNodeFactory;
 import com.oracle.graal.python.builtins.objects.type.PythonBuiltinClass;
 import com.oracle.graal.python.builtins.objects.type.TypeNodes.CheckCompatibleForAssigmentNode;
@@ -779,4 +780,19 @@ PNone initSubclass(@SuppressWarnings("unused") Object self) {
             return PNone.NONE;
         }
     }
+
+    @Builtin(name = __SUBCLASSHOOK__, minNumOfPositionalArgs = 1, declaresExplicitSelf = true, takesVarArgs = true, takesVarKeywordArgs = true, isClassmethod = true)
+    @GenerateNodeFactory
+    abstract static class SubclassHookNode extends PythonVarargsBuiltinNode {
+        @Specialization
+        @SuppressWarnings("unused")
+        static Object notImplemented(Object self, Object[] arguments, PKeyword[] keywords) {
+            return PNotImplemented.NOT_IMPLEMENTED;
+        }
+
+        @Override
+        public Object varArgExecute(VirtualFrame frame, Object self, Object[] arguments, PKeyword[] keywords) throws VarargsBuiltinDirectInvocationNotSupported {
+            return PNotImplemented.NOT_IMPLEMENTED;
+        }
+    }
 }