title: conda stuck on Proceed ([y]/n)? when updating packages in ipython console
body: <p>I just downloaded Anaconda 4.2.0 (with python 3.5.2) for Mac OS X. Whenever I try to update any packages etc, my ipython console presents the package dependencies and displays "Proceed ([y]/n)?" but does not take any inputs. E.g. I press enter, or y-enter etc. and nothing happens. Here's an example:</p>
  
  <pre><code>!conda create -n graphlab-env python=2.7 anaconda
  Fetching package metadata .......
  Solving package specifications: ..........
  
  Package plan for installation in environment /Users/Abhijit/anaconda/envs/graphlab-env:
  
  The following packages will be downloaded:
  
      package                    |            build
      ---------------------------|-----------------
      python-2.7.12              |                1         9.5 MB
      _license-1.1               |           py27_1          80 KB
      alabaster-0.7.9            |           py27_0          11 KB
      anaconda-clean-1.0.0       |           py27_0           3 KB
  .
  .
  .
      nbpresent-3.0.2            |           py27_0         463 KB
      anaconda-4.2.0             |      np111py27_0           6 KB
      ------------------------------------------------------------
                                             Total:       143.9 MB
  
  The following NEW packages will be INSTALLED:
  
      _license:           1.1-py27_1         
      _nb_ext_conf:       0.3.0-py27_0       
      alabaster:          0.7.9-py27_0       
      anaconda:           4.2.0-np111py27_0  
      anaconda-clean:     1.0.0-py27_0       
  .
  .
  .
      yaml:               0.1.6-0            
      zlib:               1.2.8-3            
  
  Proceed ([y]/n)? 
  </code></pre>
  
  <p>It won't respond after this step. When I enter 'Ctrl-C' it breaks out of this loop. I have tried Shift-Enter, Alt-Enter, Ctrl-Enter, Cmd-Enter etc but no luck. Tearing my hair out over this. Am I missing something?</p>