STINNER Victor (haypo)'s patch for bug 3988, Byte warning mode and b'' != ''

Also, his patch to runtests.sh to pass the -bb option (issue 4125).

Lib/test/test_bytes.py

@@ -9,6 +9,7 @@ import os
 import re
 import sys
 import copy
+import operator
 import pickle
 import tempfile
 import unittest
@@ -863,6 +864,17 @@ class AssortedBytesTest(unittest.TestCase):
         b = bytearray()
         self.failIf(b.replace(b'', b'') is b)
 
+    def test_compare(self):
+        if sys.flags.bytes_warning:
+            warnings.simplefilter('error', BytesWarning)
+            self.assertRaises(BytesWarning, operator.eq, b'', '')
+            self.assertRaises(BytesWarning, operator.ne, b'', '')
+            self.assertRaises(BytesWarning, operator.eq, bytearray(b''), '')
+            self.assertRaises(BytesWarning, operator.ne, bytearray(b''), '')
+        else:
+            # raise test.support.TestSkipped("BytesWarning is needed for this test: use -bb option")
+            pass
+
     # Optimizations:
     # __iter__? (optimization)
     # __reversed__? (optimization)

Objects/bytearrayobject.c

@@ -939,7 +939,7 @@ bytes_richcompare(PyObject *self, PyObject *other, int op)
        error, even if the comparison is for equality. */
     if (PyObject_IsInstance(self, (PyObject*)&PyUnicode_Type) ||
         PyObject_IsInstance(other, (PyObject*)&PyUnicode_Type)) {
-        if (Py_BytesWarningFlag && op == Py_EQ) {
+        if (Py_BytesWarningFlag && (op == Py_EQ || op == Py_NE)) {
             if (PyErr_WarnEx(PyExc_BytesWarning,
                             "Comparison between bytearray and string", 1))
                 return NULL;

Objects/bytesobject.c

@@ -818,7 +818,7 @@ string_richcompare(PyBytesObject *a, PyBytesObject *b, int op)
 
 	/* Make sure both arguments are strings. */
 	if (!(PyBytes_Check(a) && PyBytes_Check(b))) {
-		if (Py_BytesWarningFlag && (op == Py_EQ) &&
+		if (Py_BytesWarningFlag && (op == Py_EQ || op == Py_NE) &&
 		    (PyObject_IsInstance((PyObject*)a,
 					 (PyObject*)&PyUnicode_Type) ||
 		    PyObject_IsInstance((PyObject*)b,