title: Cannot create virtualenv instance in python 2.7.5 because of pip installation error
body: <p>I'm trying to follow the directions on the Flask installation website but I encountered an error after I used "sudo easy_install virtualenv" to install virtual environment. Not sure </p>
  
  <pre><code>Opals-MacBook-Pro:~ opalkale$ mkdir myproject
  Opals-MacBook-Pro:~ opalkale$ cd myproject
  Opals-MacBook-Pro:myproject opalkale$ virtualenv venv
  New python executable in venv/bin/python
  Installing setuptools, pip...
    Complete output from command /Users/opalkale/myproject/venv/bin/python -c "import sys, pip; pip...ll\"] + sys.argv[1:])" setuptools pip:
    Traceback (most recent call last):
    File "&lt;string&gt;", line 1, in &lt;module&gt;
    File "/Library/Python/2.7/site-packages/virtualenv-1.11-py2.7.egg/virtualenv_support/pip-1.5-py2.py3-none-any.whl/pip/__init__.py", line 9, in &lt;module&gt;
    File "/Library/Python/2.7/site-packages/virtualenv-1.11-py2.7.egg/virtualenv_support/pip-1.5-py2.py3-none-any.whl/pip/log.py", line 8, in &lt;module&gt;
    File "/Library/Python/2.7/site-packages/virtualenv-1.11-py2.7.egg/virtualenv_support/setuptools-2.0.2-py2.py3-none-any.whl/pkg_resources.py", line 2696, in &lt;module&gt;
    File "/Library/Python/2.7/site-packages/virtualenv-1.11-py2.7.egg/virtualenv_support/setuptools-2.0.2-py2.py3-none-any.whl/pkg_resources.py", line 429, in __init__
    File "/Library/Python/2.7/site-packages/virtualenv-1.11-py2.7.egg/virtualenv_support/setuptools-2.0.2-py2.py3-none-any.whl/pkg_resources.py", line 443, in add_entry
    File "/Library/Python/2.7/site-packages/virtualenv-1.11-py2.7.egg/virtualenv_support/setuptools-2.0.2-py2.py3-none-any.whl/pkg_resources.py", line 1722, in find_in_zip
    File "/Library/Python/2.7/site-packages/virtualenv-1.11-py2.7.egg/virtualenv_support/setuptools-2.0.2-py2.py3-none-any.whl/pkg_resources.py", line 1298, in has_metadata
    File "/Library/Python/2.7/site-packages/virtualenv-1.11-py2.7.egg/virtualenv_support/setuptools-2.0.2-py2.py3-none-any.whl/pkg_resources.py", line 1614, in _has
    File "/Library/Python/2.7/site-packages/virtualenv-1.11-py2.7.egg/virtualenv_support/setuptools-2.0.2-py2.py3-none-any.whl/pkg_resources.py", line 1488, in _zipinfo_name
  AssertionError: /Library/Python/2.7/site-packages/virtualenv-1.11-py2.7.egg/EGG-INFO/PKG-INFO is not a subpath of /Library/Python/2.7/site-packages/virtualenv-1.11-py2.7.egg/virtualenv_support/setuptools-2.0.2-py2.py3-none-any.whl/
  ----------------------------------------
  ...Installing setuptools, pip...done.
  Traceback (most recent call last):
    File "/usr/local/bin/virtualenv", line 8, in &lt;module&gt;
  load_entry_point('virtualenv==1.11', 'console_scripts', 'virtualenv')()
  File "/Library/Python/2.7/site-packages/virtualenv-1.11-py2.7.egg/virtualenv.py", line 820, in main
  symlink=options.symlink)
    File "/Library/Python/2.7/site-packages/virtualenv-1.11-py2.7.egg/virtualenv.py", line 988, in create_environment
  install_wheel(to_install, py_executable, search_dirs)
    File "/Library/Python/2.7/site-packages/virtualenv-1.11-py2.7.egg/virtualenv.py", line 956, in install_wheel
  'PIP_NO_INDEX': '1'
    File "/Library/Python/2.7/site-packages/virtualenv-1.11-py2.7.egg/virtualenv.py", line 898, in call_subprocess
  % (cmd_desc, proc.returncode))
  OSError: Command /Users/opalkale/myproject/venv/bin/python -c "import sys, pip; pip...ll\"] + sys.argv[1:])" setuptools pip failed with error code 1
  </code></pre>