Use explicit bytestring with struct.unpack

jkseppan · jkseppan · commit 5085af73a1bf · 2015-07-09T10:05:09.000+03:00
Apparently needed in Python 2.6.
diff --git a/lib/matplotlib/backends/backend_pdf.py b/lib/matplotlib/backends/backend_pdf.py
@@ -1295,7 +1295,7 @@ def _writePng(self, data):
         while True:
             n = buffer.readinto(header)
             assert n == 8
-            length, type = struct.unpack('!L4s', header)
+            length, type = struct.unpack(b'!L4s', header)
             if type == b'IDAT':
                 data = bytearray(length)
                 n = buffer.readinto(data)
