Installing python-glanceclient using Brew on Mac OS X 10.10

I was getting clang errors on ffi.h when trying to install python-glanceclient using pip:

$ pip install python-glanceclient
Installing collected packages: python-glanceclient, cryptography, jsonschema, jsonpatch, cffi, jsonpointer, pycparser
Running install for cryptography
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
Cleaning up...
Command /usr/local/opt/python/bin/python2.7 -c "import setuptools, tokenize;__file__='/private/tmp/pip_build_brew/cryptography/';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-jghJZG-record/install-record.txt --single-version-externally-managed --compile failed with error code 1 in /private/tmp/pip_build_brew/cryptography
Storing debug log for failure in /Users/brew/.pip/pip.log

A fix that seems to work is manually installing libffi and exporting PKG_CONFIG_PATH pointing to it:

$ brew install pkg-config libffi
$ export PKG_CONFIG_PATH=/usr/local/Cellar/libffi/3.0.13/lib/pkgconfig/
$ pip install cffi
$ pip install python-glanceclient
$ glance --version