Merge pull request #388 from megies/mention_pillow

mention pillow when PIL is not found (instead of linking to long-dead PIL page)

Author: WeatherGod

lib/mpl_toolkits/basemap/__init__.py

@@ -4020,7 +4020,9 @@ def warpimage(self,image="bluemarble",scale=None,**kwargs):
             try:
                 import Image
             except ImportError:
-                raise ImportError('warpimage method requires PIL (http://www.pythonware.com/products/pil)')
+                msg = ('warpimage method requires PIL '
+                       '(http://pillow.readthedocs.io)')
+                raise ImportError(msg)
 
         from matplotlib.image import pil_to_array
         if self.celestial: