title: After installing Anaconda, I get constant "KeyError: 'PYTHONPATH'" messages
body: <p>After installing Anaconda for Python 3.4 on my Mac I get constant messages saying: </p>
  
  <pre><code>Error in sitecustomize; set PYTHONVERBOSE for traceback: 
  KeyError: 'PYTHONPATH'
  </code></pre>
  
  <p>As suggested by a user on another question, I used </p>
  
  <pre><code>PYTHONVERBOSE=1 conda update --all
  </code></pre>
  
  <p>And received the traceback:</p>
  
  <pre><code>Traceback (most recent call last):
    File "/Users/user/anaconda/lib/python3.4/site.py", line 506, in execsitecustomize
      import sitecustomize
    File "&lt;frozen importlib._bootstrap&gt;", line 2237, in _find_and_load
    File "&lt;frozen importlib._bootstrap&gt;", line 2226, in _find_and_load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 1200, in _load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 1129, in _exec
    File "&lt;frozen importlib._bootstrap&gt;", line 1471, in exec_module
    File "&lt;frozen importlib._bootstrap&gt;", line 321, in _call_with_frames_removed
    File "/usr/local/lib/python2.7/site-packages/sitecustomize.py", line 15, in &lt;module&gt;
      str(sys.version_info[0]) + '.x!\n     PYTHONPATH is currently: "' + str(os.environ['PYTHONPATH']) + '"\n' +
    File "/Users/user/anaconda/lib/python3.4/os.py", line 633, in __getitem__
      raise KeyError(key) from None
  KeyError: 'PYTHONPATH'
  # destroy sitecustomize
  </code></pre>
  
  <p>I have looked around and found that 'PYTHONPATH' does not exist as a key in os.environ. </p>