[py3] Renamed next to __next__ in iterators.

See PEP 3114. `next` is retained as an alias for Python 2.

django/http/multipartparser.py

@@ -305,7 +305,7 @@ class LazyStream(object):
         out = b''.join(parts())
         return out
 
-    def next(self):
+    def __next__(self):
         """
         Used when the exact number of bytes to read is unimportant.
 
@@ -322,6 +322,8 @@ class LazyStream(object):
         self.position += len(output)
         return output
 
+    next = __next__             # Python 2 compatibility
+
     def close(self):
         """
         Used to invalidate/disable this lazy stream.
@@ -376,7 +378,7 @@ class ChunkIter(object):
         self.flo = flo
         self.chunk_size = chunk_size
 
-    def next(self):
+    def __next__(self):
         try:
             data = self.flo.read(self.chunk_size)
         except InputStreamExhausted:
@@ -386,6 +388,8 @@ class ChunkIter(object):
         else:
             raise StopIteration()
 
+    next = __next__             # Python 2 compatibility
+
     def __iter__(self):
         return self
 
@@ -400,12 +404,14 @@ class InterBoundaryIter(object):
     def __iter__(self):
         return self
 
-    def next(self):
+    def __next__(self):
         try:
             return LazyStream(BoundaryIter(self._stream, self._boundary))
         except InputStreamExhausted:
             raise StopIteration()
 
+    next = __next__             # Python 2 compatibility
+
 class BoundaryIter(object):
     """
     A Producer that is sensitive to boundaries.
@@ -441,7 +447,7 @@ class BoundaryIter(object):
     def __iter__(self):
         return self
 
-    def next(self):
+    def __next__(self):
         if self._done:
             raise StopIteration()
 
@@ -482,6 +488,8 @@ class BoundaryIter(object):
                 stream.unget(chunk[-rollback:])
                 return chunk[:-rollback]
 
+    next = __next__             # Python 2 compatibility
+
     def _find_boundary(self, data, eof = False):
         """
         Finds a multipart boundary in data.