title: Package libffi was not found in the pkg-config search path REDHAT6.5
body: <p>I am trying to run setup.py related to a proprietary software installation and it has dependencies on libffi.</p>
  
  <p>Since its Redhat 6.5 the python version was 2.6 and i installed python 2.7.</p>
  
  <p>libffi was already installed and when i create a virtualenv and try installing the software by running the setup.py i get the following error:</p>
  
  <pre><code>No package 'libffi' found
  Package libffi was not found in the pkg-config search path.
  Perhaps you should add the directory containing `libffi.pc'
  to the PKG_CONFIG_PATH environment variable
  No package 'libffi' found
  c/_cffi_backend.c:15:17: error: ffi.h: No such file or directory
  In file included from c/_cffi_backend.c:63:
  
  yum list libffi
  Loaded plugins: product-id, refresh-packagekit, security, subscription-manager
  This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.
  Installed Packages
  libffi.x86_64                  3.0.5-3.2.el6                   @anaconda-RedHatEnterpriseLinux-201311111358.x86_64/6.5
  Available Packages
  libffi.i686                    3.0.5-3.2.el6                   rhel-local   
  </code></pre>
  
  <p>My query is how do we modify the pkg-config search path.
  to point to libffi.pc?</p>