title: Flask's url_for does not quote slashes
body: <p>I'm trying out Flash and Jinja2 to see if I can use them for my next projects.</p>
  
  <p>However, I'm stuck here:<br>
  I have a product route (<code>@app.route('/product/&lt;prod&gt;/')</code>) but when I use in another Jinja2 template this expression <code>{{ url_for('product', prod='abc/def') }}</code> it builds this URL: <code>/product/abc/def/</code> instead of <code>/product/abc%2Fdef/</code>...</p>
  
  <p>How can I tell Flask to also encode the <code>/</code> when building URLs?</p>
  
  <p>BTW, using the <code>replace</code> filter does not work since it will also replace all the other slashes.</p>
  
  <p>Thanks</p>