Remove case for when _imaging module is not present

src/PIL/PngImagePlugin.py

@@ -92,13 +92,9 @@ def _safe_zlib_decompress(s):
 class ChunkStream(object):
 
     def __init__(self, fp):
-
         self.fp = fp
         self.queue = []
 
-        if not hasattr(Image.core, "crc32"):
-            self.crc = self.crc_skip
-
     def read(self):
         "Fetch a new chunk. Returns header information."
         cid = None
@@ -160,7 +156,7 @@ class ChunkStream(object):
         "Read checksum.  Used if the C module is not present"
 
         self.fp.read(4)
-
+        
     def verify(self, endchunk=b"IEND"):
 
         # Simple approach; just calculate checksum for all remaining