aslo check for the unpremultiply_argb_in_place cython code since we w…

…ill need it

git-svn-id: https://xpra.org/svn/Xpra/trunk@4152 3bb7dfac-3a0b-4e04-842a-767bc560f471

src/xpra/client/gtk2/client.py

@@ -88,6 +88,8 @@ def get_core_encodings(self):
                 #check for bytearray which is used by PixmapBacking
                 #to unpremultiply rgb32 data
                 bytearray("")
+                from xpra.codecs.argb.argb import unpremultiply_argb_in_place
+                assert unpremultiply_argb_in_place
                 encodings.append("rgb32")
             except:
                 pass