fix structseq attribute setter error message

2 files changed, 15 insertions, 2 deletions

diff --git a/lib_pypy/_structseq.py b/lib_pypy/_structseq.py
index 8ac47ddd84..3a817fef95 100644
--- a/lib_pypy/_structseq.py
+++ b/lib_pypy/_structseq.py
@@ -104,8 +104,11 @@ def structseq_reduce(self):
     return type(self), (tuple(self), self.__dict__)
 
 def structseq_setattr(self, attr, value):
-    raise AttributeError("%r object has no attribute %r" % (
-        self.__class__.__name__, attr))
+    if attr not in type(self).__dict__:
+        raise AttributeError("%r object has no attribute %r" % (
+            self.__class__.__name__, attr))
+    else:
+        raise TypeError("readonly attribute")
 
 def structseq_repr(self):
     fields = {}
diff --git a/pypy/module/sys/test/test_sysmodule.py b/pypy/module/sys/test/test_sysmodule.py
index cf0812ae93..2a8d70f710 100644
--- a/pypy/module/sys/test/test_sysmodule.py
+++ b/pypy/module/sys/test/test_sysmodule.py
@@ -141,6 +141,16 @@ class AppTestAppSysTests:
         exc = raises(SystemExit, sys.exit, (1, 2, 3))
         assert exc.value.code == (1, 2, 3)
 
+    def test_sys_flags(self):
+        import sys
+        # sanity check
+        assert sys.flags.optimize is not None
+        # make sure the flags are read-only
+        exc = raises(TypeError, 'sys.flags.optimize = 3')
+        assert 'readonly' in str(exc.value)
+        raises(AttributeError, 'sys.flags.not_a_sys_flag = 2')
+        
+
 
 class AppTestSysModulePortedFromCPython: