title: Python Multiprocessing - TypeError: Pickling an AuthenticationString object is disallowed for security reasons
body: <p>I'm having the following Problem. I want to implement a web crawler, so far this worked but it was so slow, that I tried to use multiprocessing for fetching the URLs.
  Unfortunately I'm not very experienced at this field.
  After some reading the easiest way seemed to me to use the <code>map</code> method from <code>multiprocessing.pool</code> for this.</p>
  
  <p>But I constantly get the following error:</p>
  
  <pre><code>TypeError: Pickling an AuthenticationString object is disallowed for security reasons
  </code></pre>
  
  <p>I found very few cases with the same error and they unfortunately did not help me.</p>
  
  <p>I created a stripped version of my code which can reproduce the error:</p>
  
  <pre><code>import multiprocessing
  
  class TestCrawler:
      def __init__(self):
          self.m = multiprocessing.Manager()
          self.queue = self.m.Queue()
          for i in range(50):
              self.queue.put(str(i))
          self.pool = multiprocessing.Pool(6)
  
  
  
      def mainloop(self):
          self.process_next_url(self.queue)
  
          while True:
              self.pool.map(self.process_next_url, (self.queue,))                
  
      def process_next_url(self, queue):
          url = queue.get()
          print(url)
  
  
  c = TestCrawler()
  c.mainloop()
  </code></pre>
  
  <p>I would be very thankful about any help or suggestion!</p>