make assigning to a bytes literal a syntax error (closes #11506)

Lib/test/test_syntax.py

@@ -67,6 +67,10 @@ SyntaxError: can't assign to literal
 Traceback (most recent call last):
 SyntaxError: can't assign to literal
 
+>>> b"" = 1
+Traceback (most recent call last):
+SyntaxError: can't assign to literal
+
 >>> `1` = 1
 Traceback (most recent call last):
 SyntaxError: invalid syntax

Misc/NEWS

@@ -45,6 +45,9 @@ Core and Builtins
 - Issue #5587: add a repr to dict_proxy objects.  Patch by David Stanek and
   Daniel Urban.
 
+- Issue #11506: Trying to assign to a bytes literal should result in a
+  SyntaxError.
+
 Library
 -------
 

Python/ast.c

@@ -469,6 +469,7 @@ set_context(struct compiling *c, expr_ty e, expr_context_ty ctx, const node *n)
         case Set_kind:
         case Num_kind:
         case Str_kind:
+        case Bytes_kind:
             expr_name = "literal";
             break;
         case Ellipsis_kind: