Fixed couple of "leaks" when gc is disabled

kafka/protocol/struct.py

@@ -3,6 +3,8 @@
 #from collections import namedtuple
 from io import BytesIO
 
+from kafka.util import WeakMethod
+
 from .abstract import AbstractType
 from .types import Schema
 
@@ -20,7 +22,9 @@ def __init__(self, *args, **kwargs):
             self.__dict__.update(kwargs)
 
         # overloading encode() to support both class and instance
-        self.encode = self._encode_self
+        # Without WeakMethod() this creates circular ref, which
+        # causes instances to "leak" to garbage
+        self.encode = WeakMethod(self._encode_self)
 
     @classmethod
     def encode(cls, item): # pylint: disable=E0202

kafka/vendor/selectors34.py

@@ -93,7 +93,8 @@ def __iter__(self):
         return iter(self._selector._fd_to_key)
 
 
-class BaseSelector(six.with_metaclass(ABCMeta)):
+@six.add_metaclass(ABCMeta)
+class BaseSelector(object):
     """Selector abstract base class.
 
     A selector supports registering file objects to be monitored for specific

kafka/vendor/six.py

@@ -70,7 +70,9 @@ def __len__(self):
         else:
             # 64-bit
             MAXSIZE = int((1 << 63) - 1)
-        del X
+
+        # Don't del it here, cause with gc disabled this "leaks" to garbage
+        # del X
 
 
 def _add_doc(func, doc):