Well, it worked for me: I can run development chirp natively on my Macintosh macOS Sierra 10.12.5.  I did scare myself  by removing all of my environment to start from scratch so I could describe it to you… and then it didn’t work. I’ve consolidated several notes and may have elided or duplicated some stuff. I’m sorry if it doesn’t quite work.

Here’s what finally worked (again) … starting from something like scratch in a Terminal window. I happen to have Xcode installed as well; I do not think it’s a prerequisite.

I use homebrew; it doesn’t require root privileges. Install by 
/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)”

- You can then install all the brew-installed pieces at one time now. Many dependencies get loaded as well.
brew install mercurial libxml2 libxslt pygtk gtk-mac-integration

Two of the brewed pieces need to be linked into python* 
echo /usr/local/opt/libxslt/lib/python2.7/site-packages >> /usr/local/lib/python2.7/site-packages/libxslt.pth
echo /usr/local/opt/libxml2/lib/python2.7/site-packages >> /usr/local/lib/python2.7/site-packages/libxslt.pth 

- Eventually you will use mercurial to load the chirp source ("hg clone http://d-rats.com/hg/chirp.hg")

- get pyserial. I used "sudo easy-install pyserial". Perhaps better is "pip install pyserial”

The following two python installs may be optional, based upon README in the chirp source. I did them anyway.
- install suds ('pip install suds')
- Install python-support ('pip install support’)

Start up chirp 
(cd chirp.hg; ./chirpw)
Woohoo: a window appears!

I still get warnings when I start up chirp. The following three show up before any radio data are displayed:

2017-06-25 19:02:19.088 Python[55559:1689118] *** WARNING: Method userSpaceScaleFactor in class NSView is deprecated on 10.7 and later. It should not be used in new applications. Use convertRectToBacking: instead. 
/Users/declan/chirp.hg/chirp/ui/mainapp.py:1971: Warning: invalid cast from 'GtkMenuBar' to 'GtkWindow'
  macapp.set_menu_bar(menu_bar)
/Users/declan/chirp.hg/chirp/ui/mainapp.py:1971: GtkWarning: gtk_window_add_accel_group: assertion 'GTK_IS_WINDOW (window)' failed
  macapp.set_menu_bar(menu_bar)
A serial driver seems to be needed for many radios. Mine required to use drivers from Prolific (and of course, the vendor happily supply only windoze drivers. And told me explicitly they don’t support Macintosh.) I used http://prolificusa.com/files/PL2303_MacOSX_1.6.1_20160309.zip 
FTDI drivers on Macintosh are described elsewhere
SiLabs drivers at http://www.silabs.com/documents/public/software/Mac_OSX_VCP_Driver.zip 

* These may be in other locations than shown. You may have to do a 
find /usr -name site-packages
to locate the pieces for this.

Declan Rieb, WD5EQY