title: Python's ftplib with tqdm
body: <p>I have a console script which uses <a href="https://docs.python.org/2/library/ftplib.html" rel="nofollow">ftplib</a> as a backend to get a number of files from an ftp server. I would like to use <a href="https://github.com/tqdm/tqdm" rel="nofollow">tqdm</a> to give the user some feedback provided they have a "verbose" switch on.  This <em>must</em> be optional as some users might use the script without <code>tty</code> access.</p>
  
  <p>The <a href="https://docs.python.org/2/library/ftplib.html" rel="nofollow">ftplib</a>'s <code>retrbinary</code> method takes a callback so it should be possible to hook <a href="https://github.com/tqdm/tqdm" rel="nofollow">tqdm</a> in there somehow. However, I have no idea what this callback would look like.</p>