Pushed GDAL skip condition inside test

As GDAL_VERSION is conditionnaly imported, it cannot be referenced
in skipIf decorator.

tests/gis_tests/gdal_tests/test_raster.py

@@ -54,7 +54,7 @@ from django.utils._os import upath
 from ..data.rasters.textrasters import JSON_RASTER
 
 if HAS_GDAL:
-    from django.contrib.gis.gdal import GDALRaster
+    from django.contrib.gis.gdal import GDALRaster, GDAL_VERSION
     from django.contrib.gis.gdal.raster.band import GDALBand
 
 
@@ -211,8 +211,9 @@ class GDALRasterTests(unittest.TestCase):
              12.0, 13.0, 14.0, 15.0]
         )
 
-    @unittest.skipIf(GDAL_VERSION < (1, 8, 1), "GDAL >= 1.8.1 is required for this test")
     def test_raster_transform(self):
+        if GDAL_VERSION < (1, 8, 1):
+            self.skipTest("GDAL >= 1.8.1 is required for this test")
         # Prepare tempfile and nodata value
         rstfile = tempfile.NamedTemporaryFile(suffix='.tif')
         ndv = 99