Address flake8 requirement

Author: smartlixx

lib/cartopy/data/raster/etopo1.jpg

@@ -41,6 +41,7 @@
 import cartopy.mpl.patch as cpatch
 from cartopy.mpl.slippy_image_artist import SlippyImageArtist
 from cartopy.vector_transform import vector_scalar_to_grid
+from cartopy.io import Downloader
 
 
 assert mpl.__version__ >= '1.5.1', ('Cartopy is only supported with '
@@ -1005,11 +1006,13 @@ def stock_img(self, name='ne_shaded'):
         """
         Add a standard image to the map.
 
-        Currently, there are 2 options. 
-        1: 'ne_shaded'(default) a downsampled version of the Natural Earth shaded relief raster.
-        2: 'etopo1' a downsampled version of global relief model of Earth's surface that
-        integrates land topography and ocean bathymetry. This option is the same as the etopo1 
-        from Basemap.
+        Currently, there are 2 options:
+
+        1. 'ne_shaded'(default) a downsampled version of the Natural Earth
+           shaded relief raster.
+        2. 'etopo1' a downsampled version of global relief model of Earth's
+           surface that integrates land topography and ocean bathymetry. This
+           option is the same as the etopo1 from Basemap.
         """
         if name == 'ne_shaded':
             import os
@@ -1024,8 +1027,16 @@ def stock_img(self, name='ne_shaded'):
         elif name == 'etopo1':
             import os
             source_proj = ccrs.PlateCarree()
-            fname = os.path.join(config["repo_data_dir"],
-                                 'raster', 'etopo1.jpg')
+
+            url_template = 'https://www.ngdc.noaa.gov/mgg/image/{name}.jpg'
+            target_path_template = os.path.join(config["data_dir"],
+                                                'raster', '{name}.jpg')
+            pre_downloaded_path_template = target_path_template
+            d = Downloader(url_template, target_path_template,
+                           pre_downloaded_path_template)
+            cfg = {('etopo1'): d}
+            dl = Downloader.from_config(('etopo1'), config_dict=cfg)
+            fname = dl.path({'name': 'color_etopo1_ice_low'})
 
             return self.imshow(imread(fname), origin='upper',
                                transform=source_proj,