title: Ubuntu python-dateutil install/upgrade issue. dateutil.zoneinfo.gettz returning NoneType
body: <p>I am having trouble with python dateutil.zoneinfo module.
  Note: </p>
  
  <ul>
  <li>Broken Ubuntu machine is ( Ubuntu 11.04 )</li>
  <li>Working Ubuntu machine is ( Ubuntu 11.10 )</li>
  </ul>
  
  <p><em>Broken Ubuntu machine:</em></p>
  
  <pre><code>In [1]: from dateutil import zoneinfo`
  In [2]: from_zone = zoneinfo.gettz('UTC')
  In [3]: from_zone
  </code></pre>
  
  <p><em>From a working Ubuntu machine:</em></p>
  
  <pre><code>In [1]: from dateutil import zoneinfo
  In [2]: from_zone = zoneinfo.gettz('UTC')
  In [3]: from_zone
  Out[3]: tzfile('Etc/UTC')
  </code></pre>
  
  <p>Some Python introspection.</p>
  
  <p><em>Broken Ubuntu machine:</em></p>
  
  <pre><code>In [5]: zoneinfo.ZONEINFOFILE
  </code></pre>
  
  <p><em>From a working Ubuntu machine:</em></p>
  
  <pre><code>In [4]: zoneinfo.ZONEINFOFILE
  Out[4]: '/usr/local/lib/python2.7/dist-packages/python_dateutil-1.5-py2.7.egg/dateutil/zoneinfo/zoneinfo-2010g.tar.gz'
  </code></pre>
  
  <p>More information: 
  the broken machine, has upgraded from python 2.6 to python 2.7.
  Doing a </p>
  
  <pre><code>$ locate zoneinfo
  -- snip --
  /usr/lib/pymodules/python2.6/dateutil/zoneinfo
  /usr/lib/pymodules/python2.6/dateutil/zoneinfo/__init__.py
  /usr/lib/pymodules/python2.6/dateutil/zoneinfo/__init__.pyc
  /usr/lib/pymodules/python2.7/dateutil/zoneinfo
  /usr/lib/pymodules/python2.7/dateutil/zoneinfo/__init__.py
  /usr/lib/pymodules/python2.7/dateutil/zoneinfo/__init__.pyc
  /usr/local/lib/python2.6/dist-packages/dateutil/zoneinfo
  /usr/local/lib/python2.6/dist-packages/dateutil/zoneinfo/__init__.py
  /usr/local/lib/python2.6/dist-packages/dateutil/zoneinfo/__init__.pyc
  /usr/local/lib/python2.6/dist-packages/dateutil/zoneinfo/zoneinfo-2010g.tar.gz
  /usr/local/lib/python2.6/dist-packages/dateutil/zoneinfo/zoneinfo-2011d.tar.gz
  /usr/share/zoneinfo
  /usr/share/pyshared/dateutil/zoneinfo
  -- snip --
  </code></pre>
  
  <p>I can see the issue but I am unsure about what to do about it.
  Note: I tried re-installing the python-dateutil with 'synaptic package manager' to no avail.</p>