title: Set CRS for a file read with rasterio
body: <p>I am reading a jpg image and its associated world file in Python with Rasterio like this: </p>
  
  <pre><code>import rasterio
  with rasterio.open('/path/to/file.jpg') as src:
      print(src.width, src.height)
      print(src.crs)
      print(src.indexes)
  </code></pre>
  
  <p>The image file and its associated world file are correctly read, however the CRS is undefined (<a href="https://en.wikipedia.org/wiki/World_file" rel="noreferrer">I guess that's because world file doesn't contain the CRS</a>). Here is the output:</p>
  
  <pre><code>5000 5000
  None
  (1, 2, 3)
  </code></pre>
  
  <p>How to set the CRS manually in Rasterio after reading the file?</p>