title: pip install mod_wsgi fails in virtualenv
body: <p>I'm trying to install mod_wsgi using pip in python 2.7.10 on mac os 10.12 inside a virtualenv. I intend to use it in a a Django 1.10.3.
  When I run "pip install mod_wsgi" I get the following output:</p>
  
  <pre><code>Collecting mod_wsgi
  Using cached mod_wsgi-4.5.7.tar.gz
  Complete output from command python setup.py egg_info:
  Traceback (most recent call last):
    File "&lt;string&gt;", line 1, in &lt;module&gt;
    File "/private/var/folders/sf/kdqqs98d06326180mss7hggh0000gn/T/pip-build-hgA7s1/mod-wsgi/setup.py", line 247, in &lt;module&gt;
      APR_INCLUDES = get_apr_includes().split()
    File "/private/var/folders/sf/kdqqs98d06326180mss7hggh0000gn/T/pip-build-hgA7s1/mod-wsgi/setup.py", line 219, in get_apr_includes
      stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 710, in __init__
      errread, errwrite)
    File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 1335, in _execute_child
      raise child_exception
  OSError: [Errno 2] No such file or directory
  
  ----------------------------------------
  Command "python setup.py egg_info" failed with error code 1 in /private/var/folders/sf/kdqqs98d06326180mss7hggh0000gn/T/pip-build-hgA7s1/mod-wsgi/
  </code></pre>
  
  <p>I'm new to virtualenv so it might be that I'm just missing something with how to set that up. I've tried upgrading pip, reinstalling setuptools and ez_setup via pip. </p>