title: Why won't pip install the current version of a package?
body: <p>I can't get <code>pip</code> to install the current version of <code>pydot</code> (1.0.28). Though <code>yolk</code> and <a href="https://pypi.python.org/pypi/pydot/" rel="nofollow">PyPi</a> both report this version as the available, current one, </p>
  
  <p><code>pip -U pydot</code></p>
  
  <p>gives me</p>
  
  <pre><code>Requirement already up-to-date: pydot in /Library/Python/2.7/site-packages
  Requirement already up-to-date: pyparsing in /Library/Python/2.7/site-packages (from pydot)
  Requirement already up-to-date: setuptools in /Library/Python/2.7/site-packages (from pydot)
  </code></pre>
  
  <p>forcing the current version with </p>
  
  <p><code>pip -U pydot<b>==1.0.28</b></code></p>
  
  <p>gives me</p>
  
  <pre><code>Downloading/unpacking pydot==1.0.28
    Could not find a version that satisfies the requirement pydot==1.0.28 (from versions: 1.0.2)
    Some externally hosted files were ignored (use --allow-external to allow).
  Cleaning up...
  No distributions matching the version for pydot==1.0.28
  </code></pre>
  
  <p>and even</p>
  
  <p><code>pip -U <b>--allow-external pydot</b> pydot==1.0.28</code></p>
  
  <p>gives me</p>
  
  <pre><code>Downloading/unpacking pydot==1.0.28
    Could not find a version that satisfies the requirement pydot==1.0.28 (from versions: 1.0.2)
    Some insecure and unverifiable files were ignored (use --allow-unverified pydot to allow).
  Cleaning up...
  No distributions matching the version for pydot==1.0.28
  </code></pre>