Deprecate scrapy.python.utils.FixedSGMLParser

SGML link extractor that uses it is also going to be deprecated;
sgmllib module is not available in Python 3.

scrapy/utils/python.py

@@ -10,23 +10,40 @@
 import inspect
 import weakref
 import errno
+import warnings
 from functools import partial, wraps
-from sgmllib import SGMLParser
 
+import six
 
-class FixedSGMLParser(SGMLParser):
-    """The SGMLParser that comes with Python has a bug in the convert_charref()
-    method. This is the same class with the bug fixed"""
+from scrapy.exceptions import ScrapyDeprecationWarning
 
-    def convert_charref(self, name):
-        """This method fixes a bug in Python's SGMLParser."""
-        try:
-            n = int(name)
-        except ValueError:
-            return
-        if not 0 <= n <= 127 : # ASCII ends at 127, not 255
-            return
-        return self.convert_codepoint(n)
+
+if six.PY2:
+    from sgmllib import SGMLParser
+
+    class FixedSGMLParser(SGMLParser):
+        """The SGMLParser that comes with Python has a bug in the convert_charref()
+        method. This is the same class with the bug fixed.
+
+        Warning: this class is deprecated and will be removed in future releases.
+        """
+
+        def __init__(self, *args, **kwargs):
+            warnings.warn(
+                "FixedSGMLParser is deprecated and will be removed in future releases.",
+                ScrapyDeprecationWarning
+            )
+            SGMLParser.__init__(self, *args, **kwargs)
+
+        def convert_charref(self, name):
+            """This method fixes a bug in Python's SGMLParser."""
+            try:
+                n = int(name)
+            except ValueError:
+                return
+            if not 0 <= n <= 127 : # ASCII ends at 127, not 255
+                return
+            return self.convert_codepoint(n)
 
 
 def flatten(x):