Switch to pickle protocol 4

scrapy/exporters.py

@@ -250,7 +250,7 @@ class CsvItemExporter(BaseItemExporter):
 
 class PickleItemExporter(BaseItemExporter):
 
-    def __init__(self, file, protocol=2, **kwargs):
+    def __init__(self, file, protocol=4, **kwargs):
         super().__init__(**kwargs)
         self.file = file
         self.protocol = protocol

scrapy/extensions/httpcache.py

@@ -250,7 +250,7 @@ class DbmCacheStorage:
             'headers': dict(response.headers),
             'body': response.body,
         }
-        self.db['%s_data' % key] = pickle.dumps(data, protocol=2)
+        self.db['%s_data' % key] = pickle.dumps(data, protocol=4)
         self.db['%s_time' % key] = str(time())
 
     def _read_data(self, spider, request):
@@ -317,7 +317,7 @@ class FilesystemCacheStorage:
         with self._open(os.path.join(rpath, 'meta'), 'wb') as f:
             f.write(to_bytes(repr(metadata)))
         with self._open(os.path.join(rpath, 'pickled_meta'), 'wb') as f:
-            pickle.dump(metadata, f, protocol=2)
+            pickle.dump(metadata, f, protocol=4)
         with self._open(os.path.join(rpath, 'response_headers'), 'wb') as f:
             f.write(headers_dict_to_raw(response.headers))
         with self._open(os.path.join(rpath, 'response_body'), 'wb') as f:

scrapy/extensions/spiderstate.py

@@ -26,7 +26,7 @@ class SpiderState:
     def spider_closed(self, spider):
         if self.jobdir:
             with open(self.statefn, 'wb') as f:
-                pickle.dump(spider.state, f, protocol=2)
+                pickle.dump(spider.state, f, protocol=4)
 
     def spider_opened(self, spider):
         if self.jobdir and os.path.exists(self.statefn):

scrapy/squeues.py

@@ -81,7 +81,7 @@ def _scrapy_non_serialization_queue(queue_class):
 
 def _pickle_serialize(obj):
     try:
-        return pickle.dumps(obj, protocol=2)
+        return pickle.dumps(obj, protocol=4)
     # Python <= 3.4 raises pickle.PicklingError here while
     # 3.5 <= Python < 3.6 raises AttributeError and
     # Python >= 3.6 raises TypeError