How to set the path for cairo in ubuntu-12.04?

I need to install pycairo with python3.2+.But I have error when installing the pycairo in my system, ``` Downloading/unpacking git+http://anongit.freedesktop.org/git/pycairo (from -r requirements.txt (line 7)) Cloning http://anongit.freedesktop.org/git/pycairo to /tmp/pip-ud145u-build Running setup.py egg_info for package from git+http://anongit.freedesktop.org/git/pycairo cairo >= 1.10.2 Failed Package cairo was not found in the pkg-config search path. Perhaps you should add the directory containing `cairo.pc' to the PKG_CONFIG_PATH environment variable No package 'cairo' found Complete output from command python setup.py egg_info: cairo >= 1.10.2 Failed Package cairo was not found in the pkg-config search path. Perhaps you should add the directory containing `cairo.pc' to the PKG_CONFIG_PATH environment variable No package 'cairo' found ```