OSX install instructions didn't work out of the box (SYN-358)

[matrixbot]

On OSX 10.10.2 with Xcode 6.3.1 installed, and Python 2.7.6 (barely used), I followed the instructions in README.md:

$ sudo easy_install pip
$ sudo pip install virtualenv
$ virtualenv ~/.virualenvs/synapse
$ source ~/.virtualenvs/synapse/bin/activate
$ pip install --process-dependency-links https://github.com/matrix-org/synapse/tarball/master

and got an error because libffi was missing. [if I paste the error message into here, Jira gives me a beautiful exception, I guess because of some unicode in there it doesn't understand].

I installed libffi with brew:
$ brew install pkg-config libffi

re-ran the pip command, and it worked fine.

It may be worth mentioning this in either the "Installing prerequisites on Mac OS X:" section, or the "Troubleshooting" section.

(Imported from https://matrix.org/jira/browse/SYN-358)

(Reported by @illicitonion)

[matrixbot]

Jira watchers: @dbkr @illicitonion

[matrixbot]

Are you using python from homebrew or OS X's standard python?

-- @dbkr

[matrixbot]

Response via email was that it's OS X python, which is surprising as OS X I think has libffi built in, and it's fine on my machine with neither libffi nor python from homebrew.

-- @dbkr

[hawkowl]

This is likely not an issue anymore, and if it is, people'll report it.