fixed method override check in Python 2

scrapy/spiders/__init__.py

@@ -12,6 +12,7 @@ from scrapy.utils.trackref import object_ref
 from scrapy.utils.url import url_is_from_spider
 from scrapy.utils.deprecate import create_deprecated_class
 from scrapy.exceptions import ScrapyDeprecationWarning
+from scrapy.utils.deprecate import method_is_overridden
 
 
 class Spider(object_ref):
@@ -67,7 +68,7 @@ class Spider(object_ref):
 
     def start_requests(self):
         cls = self.__class__
-        if cls.make_requests_from_url is not Spider.make_requests_from_url:
+        if method_is_overridden(cls, Spider, 'make_requests_from_url'):
             warnings.warn(
                 "Spider.make_requests_from_url method is deprecated; it "
                 "won't be called in future Scrapy releases. Please "

scrapy/utils/deprecate.py

@@ -156,3 +156,35 @@ def update_classpath(path):
                           ScrapyDeprecationWarning)
             return new_path
     return path
+
+
+def method_is_overridden(subclass, base_class, method_name):
+    """ 
+    Return True if a method named ``method_name`` of a ``base_class`` 
+    is overridden in a ``subclass``. 
+    
+    >>> class Base(object):
+    ...     def foo(self):
+    ...         pass
+    >>> class Sub1(Base):
+    ...     pass
+    >>> class Sub2(Base):
+    ...     def foo(self):
+    ...         pass
+    >>> class Sub3(Sub1):
+    ...     def foo(self):
+    ...         pass
+    >>> class Sub4(Sub2):
+    ...     pass
+    >>> method_is_overridden(Sub1, Base, 'foo')
+    False
+    >>> method_is_overridden(Sub2, Base, 'foo')
+    True
+    >>> method_is_overridden(Sub3, Base, 'foo')
+    True
+    >>> method_is_overridden(Sub4, Base, 'foo')
+    True
+    """
+    base_method = getattr(base_class, method_name)
+    sub_method = getattr(subclass, method_name)
+    return base_method.__code__ is not sub_method.__code__