fixed assertion in test_dataraster_coloring

tests/python_tests/raster_symbolizer_test.py

@@ -52,9 +52,9 @@ def test_dataraster_coloring():
     # save a png somewhere so we can see it
     save_data('test_dataraster_coloring.png', im.tostring('png'))
     imdata = im.tostring()
-    assert len(imdata) > 0
+    bytes = [imdata[i:i+4] for i in xrange(0, len(imdata), 4)]
     # we have some values in the [20,30) interval so check that they're colored
-    assert '\xff\xff\xff\x00' in imdata
+    assert '\xff\xff\x00\xff' in bytes
 
 def test_dataraster_query_point():
     srs = '+init=epsg:32630'