title: timeout not respected in request.get()
body: <p>I can't understand why with this code the <code>requests.get()</code> returns immediately error and the 10 second timeout is not respected.
  If I remove the header parameter, so only <code>requests.get(url, proxies={"http": proxy, "https": proxy}, verify=False,timeout=10)</code>,   the timeout is respected and a request is returned successfully or failure if the timeout occurs.
  I need to insert headers and a timeout too to test proxies, how to do it?</p>
  
  <pre><code>from fake_useragent import  UserAgent
  import requests
  ua = UserAgent()
  
  #get a list of proxy 
  
  for i in range(1, len(proxies)):
      # Get a proxy from the pool
      proxy = next(proxy_pool)
      print("Request #%d" % i)
      try:
          response = requests.get(url, headers=ua.random(), proxies={"http": proxy, "https": proxy}, verify=False,timeout=10)
          break
      except:
          print("Skipping. Connnection error")
  </code></pre>