title: Flask HTTPException being swallowed
body: <p>When declaring a function with <code>before_request</code> Flask is swallowing HTTPExceptions and not propagating them:</p>
  
  <pre><code>from flask import Flask
  from werkzeug.exceptions import HTTPException
  
  app = Flask(__name__)
  
  @app.before_request
  def f():
      raise HTTPException("This is not propagated")
  
  @app.route('/')
  def test():
      return 'This is a view'
  
  
  if __name__ == '__main__':
      app.run()
  </code></pre>
  
  <p>The console shows no Exception:</p>
  
  <pre><code>$ python flask_test1.py
   * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
  127.0.0.1 - - [02/Jun/2016 15:01:31] "GET / HTTP/1.1" 200 -
  </code></pre>
  
  <p>The Browser shows:</p>
  
  <pre><code>Unknown Error
  
  This is not propagated
  </code></pre>
  
  <p>Is there a way to force it ? A setting I need to specify, or should I interface Werkzeug HTTPExceptions and raise custom made Exceptions ?</p>