Issue #25262. Added support for BINBYTES8 opcode in Python implementation of
unpickler.  Highest 32 bits of 64-bit size for BINUNICODE8 and BINBYTES8
opcodes no longer silently ignored on 32-bit platforms in C implementation.
diff --git a/Lib/pickle.py b/Lib/pickle.py
index 67382ae..c7298af 100644
--- a/Lib/pickle.py
+++ b/Lib/pickle.py
@@ -1204,6 +1204,14 @@
         self.append(str(self.read(len), 'utf-8', 'surrogatepass'))
     dispatch[BINUNICODE8[0]] = load_binunicode8
 
+    def load_binbytes8(self):
+        len, = unpack('<Q', self.read(8))
+        if len > maxsize:
+            raise UnpicklingError("BINBYTES8 exceeds system's maximum size "
+                                  "of %d bytes" % maxsize)
+        self.append(self.read(len))
+    dispatch[BINBYTES8[0]] = load_binbytes8
+
     def load_short_binstring(self):
         len = self.read(1)[0]
         data = self.read(len)