code: def get_bareground_fn():
      
      bg_fn = os.path.join(datadir, 'bare2010/bare2010.vrt')
      if not os.path.exists(bg_fn):
          cmd = ['get_bareground.sh',]
          sys.exit("Missing bareground data source. If already downloaded, specify correct datadir. If not, run `%s` to download" % cmd[0])
          #subprocess.call(cmd)
      return bg_fn
docs: Calls external shell script `get_bareground.sh` to fetch:
  
      ~2010 global bare ground, 30 m
  
      Note: unzipped file size is 64 GB! Original products are uncompressed, and tiles are available globally (including empty data over ocean)
  
      The shell script will compress all downloaded tiles using lossless LZW compression.
  
      http://landcover.usgs.gov/glc/BareGroundDescriptionAndDownloads.php