title: python virtualenv - some python core libraries are missing
body: <p>I'm trying to set-up a virtualenv with Python 2.6.6 on CentOS 5.
  I've already Python 2.6.6 installed in my home directory, working well.</p>
  
  <p>However, when I try to set-up a virtualenv, I got the following error (cf. end for full log):</p>
  
  <pre><code>ImportError: No module named _md5
  </code></pre>
  
  <p>By looking at other threads, this errors occurs when changing python version on <strong>existing</strong> virtual env, which is not my case: I trying to create a new one.</p>
  
  <p>Because this error occurs when installing setuptools, I juste commented few lines in virtualenv.py source (around l.907), so it's just installing Python.
  Then, creation of virtualenv is fine, however, many core Python libraries are missing.</p>
  
  <pre><code># Creating virtualenv
  $ pwd
  /home/myhome/tmp/virtualenv-1.6.4
  $ python virtualenv.py --no-site-packages myenv
  New python executable in myenv/bin/python
  
  # Loading module outside virtualenv
  $ python -c 'import time'
  
  # Loading module inside virtualenv
  $ source ve/bin/activate
  $ python -c 'import time'
  Traceback (most recent call last):
    File "&lt;string&gt;", line 1, in &lt;module&gt;
  ImportError: No module named time
  </code></pre>
  
  <p>I really don't get the point! Python libraries are just files to copy, right?</p>
  
  <hr>
  
  <p>Full log:</p>
  
  <pre><code>$ virtualenv --no-site-packages myenv
  New python executable in myenv/bin/python2.6
  Also creating executable in myenv/bin/python
  Installing setuptools.............
    Complete output from command /home/myhome/myenv/bin/python2.6 -c "#!python
  \"\"\"Bootstra...sys.argv[1:])
  
  " --always-copy -U setuptools:
    -c:67: DeprecationWarning: the md5 module is deprecated; use hashlib instead
  Traceback (most recent call last):
    File "&lt;string&gt;", line 67, in &lt;module&gt;
    File "/home/myhome/lib/python2.6/md5.py", line 10, in &lt;module&gt;
      from hashlib import md5
    File "/home/myhome/lib/python2.6/hashlib.py", line 136, in &lt;module&gt;
      md5 = __get_builtin_constructor('md5')
    File "/home/myhome/lib/python2.6/hashlib.py", line 63, in __get_builtin_constructor
      import _md5
  ImportError: No module named _md5
  ----------------------------------------
  ...Installing setuptools...done.
  Traceback (most recent call last):
    File "/home/myhome/bin/virtualenv", line 8, in &lt;module&gt;
      load_entry_point('virtualenv==1.6.4', 'console_scripts', 'virtualenv')()
    File "/home/myhome/lib/python2.6/site-packages/virtualenv-1.6.4-py2.6.egg    /virtualenv.py", line 810, in main
      never_download=options.never_download)
    File "/home/myhome/lib/python2.6/site-packages/virtualenv-1.6.4-py2.6.egg/virtualenv.py", line 910, in create_environment
      search_dirs=search_dirs, never_download=never_download)
    File "/home/myhome/lib/python2.6/site-packages/virtualenv-1.6.4-py2.6.egg/virtualenv.py", line 603, in install_setuptools
      search_dirs=search_dirs, never_download=never_download)
    File "/home/myhome/lib/python2.6/site-packages/virtualenv-1.6.4-py2.6.egg/virtualenv.py", line 577, in _install_req
  cwd=cwd)
    File "/home/myhome/lib/python2.6/site-packages/virtualenv-1.6.4-py2.6.egg/virtualenv.py", line 878, in call_subprocess
      % (cmd_desc, proc.returncode))
  OSError: Command /home/myhome/myenv/bin/python2.6 -c "#!python
  \"\"\"Bootstra...sys.argv[1:])
  
  " --always-copy -U setuptools failed with error code 1
  </code></pre>