bpo-39988: Remove ast.AugLoad and ast.AugStore node classes. (GH-19038)

Python/ast.c

@@ -71,10 +71,6 @@ expr_context_name(expr_context_ty ctx)
         return "Store";
     case Del:
         return "Del";
-    case AugLoad:
-        return "AugLoad";
-    case AugStore:
-        return "AugStore";
     default:
         Py_UNREACHABLE();
     }
@@ -1099,14 +1095,7 @@ set_context(struct compiling *c, expr_ty e, expr_context_ty ctx, const node *n)
 {
     asdl_seq *s = NULL;
 
-    /* The ast defines augmented store and load contexts, but the
-       implementation here doesn't actually use them.  The code may be
-       a little more complex than necessary as a result.  It also means
-       that expressions in an augmented assignment have a Store context.
-       Consider restructuring so that augmented assignment uses
-       set_context(), too.
-    */
-    assert(ctx != AugStore && ctx != AugLoad);
+    /* Expressions in an augmented assignment have a Store context. */
 
     switch (e->kind) {
         case Attribute_kind: