$ uname -a
Darwin MACBOX.local 13.3.0 Darwin Kernel Version 13.3.0: Tue Jun  3 21:27:35 PDT 2014; root:xnu-2422.110.17~1/RELEASE_X86_64 x86_64
$ python -V
Python 2.7.7
$ pip -V
pip 1.5.6 from /Users/chris.rebert/envs/restfulgit/lib/python2.7/site-packages (python 2.7)
$ pip install pygit2
Downloading/unpacking pygit2
  Downloading pygit2-0.21.0.tar.gz (unknown size): 150kB downloaded
  Running setup.py (path:/Users/chris.rebert/envs/restfulgit/build/pygit2/setup.py) egg_info for package pygit2
    Traceback (most recent call last):
      File "<string>", line 17, in <module>
      File "/Users/chris.rebert/envs/restfulgit/build/pygit2/setup.py", line 178, in <module>
        from ffi import ffi
      File "pygit2/ffi.py", line 34, in <module>
        from cffi import FFI
    ImportError: No module named cffi
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):

  File "<string>", line 17, in <module>

  File "/Users/chris.rebert/envs/restfulgit/build/pygit2/setup.py", line 178, in <module>

    from ffi import ffi

  File "pygit2/ffi.py", line 34, in <module>

    from cffi import FFI

ImportError: No module named cffi

----------------------------------------
Cleaning up...
Command python setup.py egg_info failed with error code 1 in /Users/chris.rebert/envs/restfulgit/build/pygit2
Storing debug log for failure in /Users/chris.rebert/.pip/pip.log
$ # Okay, maybe if I install cffi manually beforehand?
$ pip install cffi
<installation of cffi succeeds>
$ pip install pygit2
Downloading/unpacking pygit2
  Downloading pygit2-0.21.0.tar.gz (unknown size): 150kB downloaded
  Running setup.py (path:/Users/chris.rebert/envs/restfulgit/build/pygit2/setup.py) egg_info for package pygit2

Requirement already satisfied (use --upgrade to upgrade): cffi in /Users/chris.rebert/envs/restfulgit/lib/python2.7/site-packages (from pygit2)
Requirement already satisfied (use --upgrade to upgrade): pycparser in /Users/chris.rebert/envs/restfulgit/lib/python2.7/site-packages (from cffi->pygit2)
Installing collected packages: pygit2
  Running setup.py install for pygit2
    building '_pygit2' extension
<snip>
<the pygit2 installation succeeds this time>