title: Reinstalling requirement file using pip
body: <p>I try to reinstall requirements for my project using pip but I get this error. There is a previous failed installation. how can I delete it and proceed ?</p>
  
  <pre><code>E:\projects\project course\tkz&gt;pip install -r requirements.txt
  Downloading/unpacking Django==1.5.4 (from -r requirements.txt (line 1))
  pip can't proceed with requirement 'Django==1.5.4 (from -r requirements.txt (lin
  e 1))' due to a pre-existing build directory.
  location: c:\users\sina\appdata\local\temp\pip_build_sina\Django
  This is likely due to a previous installation that failed.
  pip is being responsible and not assuming it can delete this.
  Please delete it and try again.
  
  Cleaning up...
  </code></pre>