title: Can pip install a python egg via a local package tar.gz file
body: <p>In my dev environment, due to some networking problems, when I run:</p>
  
  <pre><code>(my-virt-env)$ pip install lxml
  </code></pre>
  
  <p>It always fails due to:</p>
  
  <pre><code>Downloading/unpacking lxml
    Downloading lxml-3.1.2.tar.gz (3.3Mb): 1.2Mb downloaded
  Exception:
  Traceback (most recent call last):
    blablabla
  error: [Errno 104] Connection reset by peer
  </code></pre>
  
  <p>Then I downloaded lxml-3.1.2.tar.gz from somewhere else and used an usb key to copy it over. Is there anyway I can tell pip not bother to go to the Internet for this package, just install it via the local tar.gz? So I can do something like:</p>
  
  <pre><code>(my-virt-env)$ pip install ${local_path}/lxml*.tar.gz
  </code></pre>
  
  <p>tried this command, I get very long error message:</p>
  
  <pre><code>pip install /home/shengjie/Downloads/lxml-3.1.2.tar.gz 
  Unpacking /home/shengjie/Downloads/lxml-3.1.2.tar.gz
    Running setup.py egg_info for package from file:///home/shengjie/Downloads/lxml-3.1.2.tar.gz
      /usr/lib/python2.7/distutils/dist.py:267: UserWarning: Unknown distribution option: 'bugtrack_url'
        warnings.warn(msg)
      Building lxml version 3.1.2.
      Building without Cython.
      ERROR: /bin/sh: 1: xslt-config: not found
  
      ** make sure the development packages of libxml2 and libxslt are installed **
      ......................
      bla bla bla
      ......................
  
  /tmp/pip-Vg13dM-build/src/lxml/includes/etree_defs.h:9:31: fatal error: libxml/xmlversion.h: No such file or directory
  
  compilation terminated.
  
  error: command 'gcc' failed with exit status 1
  
  
  I am running Ubuntu, I know you can run `apt-get install python-lxml` and get it installed on your box. But that doesn't work for my case as I want install it in my virtual env: `my-virt-env`. 
  </code></pre>