python-glanceclient - error "No package 'libffi' found

[root@node1 /]# yum install python-pip -y

pip install python-novaclient
pip install python-ceilometerclient
pip install python-cinderclient
pip install python-glanceclient   - has error when i install
pip install python-heatclient
pip install python-keystoneclient
pip install python-neutronclient
pip install python-swiftclient
pip install python-troveclient

when isntall
pip install python-glanceclient
http://lkubaski.wordpress.com/2012/05/19/compiling-glib-on-centos/

Consider adjusting the PKG_CONFIG_PATH environment variable if you
installed software in a non-standard prefix.
 
Alternatively, you may set the environment variables LIBFFI_CFLAGS
and LIBFFI_LIBS to avoid the need to call pkg-config.
See the pkg-config man page for more details.

download  libffi-devel-3.0.5-3.2.el6.x86_64.rpm
rpm -ivh libffi-devel-3.0.5-3.2.el6.x86_64.rpm
[root@node1 tmp]# rpm -qa|grep libffi
libffi-devel-3.0.5-3.2.el6.x86_64
libffi-3.0.5-3.2.el6.x86_64
[root@node1 tmp]#

after that another error show not find gcc directory...so try to install following pk:

#yum install python-setuptools gcc python-devel openssl-devel libxml2-devel  libxslt-devel