Initial commit of Python queries and QL libraries.

python/ql/src/Classes/SlotsInOldStyleClass.ql

@@ -0,0 +1,18 @@
+/**
+ * @name '__slots__' in old-style class
+ * @description Overriding the class dictionary by declaring '__slots__' is not supported by old-style
+ *              classes.
+ * @kind problem
+ * @problem.severity error
+ * @tags portability
+ *       correctness
+ * @sub-severity low
+ * @precision very-high
+ * @id py/slots-in-old-style-class
+ */
+
+import python
+
+from ClassObject c
+where not c.isNewStyle() and c.declaresAttribute("__slots__") and not c.failedInference()
+select c, "Using __slots__ in an old style class just creates a class attribute called '__slots__'"