title: gdal.Translate convert batch asc to geotiff
body: <p>I have a batch of asc files which i want to mosaic them together and get one tif as output.</p>
  
  <p>I tried with gdal.BuildVRT to build a vrt file first and use gdal.Translate to convert the vrt file to geotiff.</p>
  
  <pre><code>  import os
    import gdal
    import glob
    from osgeo import osr
    path = 'C:\\Data\\asc files\\'
    os.chdir(path)
    gdal.BuildVRT('out.vrt',glob.glob(path+'\\*.asc'))
    gdal.Translate('out.tif','out.vrt',format='gtiff')
  </code></pre>
  
  <p>error occurred at gdal.Translate, 'ValueError: Received a NULL pointer.'</p>