Clearly the first thing to do was take the Air off the 'Net and back it up. Connecting the backup disk and starting a Time Machine backup saw it identify about 75,000 files of the 1,500,000 on y hard disk needed backing up. When the backup phase started it took about five minutes to get to "3k of 4.5GB backed up" and I realized I had a problem.
StackOverflow suggested I consider repairing the Time Machine disk. That's another hour I shall never see again, but at least Disk Utility gave the volume a clean bill of health, so I restarted the Time Machine backup and this time (hallelujah!) it ran. I then ran the Migration Assistant on the new (receiving) Mac and told it to restore my account, settings, applications - the whole caboodle. Since the Assistant kindly estimated this would take at least two hours and fifteen minutes I decided this would be an appropriate point at which to go for a couple of drinks with my buddy Kirby.
I found the Apple Migration Assistant to be quite friendly (disclaimer: I have always previously used manual migration procedures to switch computers and so cannot say whether Windows offers similar friendliness; if not, it should). When I returned about 90 minutes later I was delighted to find that the restore was complete (I hadn't waited around for Migration Assistant to upgrade its estimate), so I was able to log in to my newly-restored account on the updated Air.
My joy lasted as long as it took me to run a terminal session, when I saw the following delight:
Last login: Tue Nov 19 01:27:18 on tty?? Traceback (most recent call last): File "/usr/local/Cellar/python/2.7.4/Frameworks/Python.framework/Versions/2.7/lib/python2.7/runpy.py", line 162, in _run_module_as_main "__main__", fname, loader, pkg_name) File "/usr/local/Cellar/python/2.7.4/Frameworks/Python.framework/Versions/2.7/lib/python2.7/runpy.py", line 72, in _run_code exec code in run_globals File "/Library/Python/2.7/site-packages/virtualenvwrapper/hook_loader.py", line 16, in
from stevedore import ExtensionManager File "/Library/Python/2.7/site-packages/stevedore/__init__.py", line 3, in from .extension import ExtensionManager File "/Library/Python/2.7/site-packages/stevedore/extension.py", line 4, in import pkg_resources ImportError: No module named pkg_resources virtualenvwrapper.sh: There was a problem running the initialization hooks. If Python could not import the module virtualenvwrapper.hook_loader, check that virtualenv has been installed for VIRTUALENVWRAPPER_PYTHON=/usr/local/bin/python and that PATH is set properly. AirHead:~ sholden$
Not exactly what you want to see when you log in, but at least indicating the the error was probably with my virtual environments. Fortunately it was quite easy to fix this daunting error message by doing a brew install python after uninstalling the previously installed version (thereby achieving an upgrade from 2.7.2 to 2.7.5). Since my account is set to prefer /usr/local/bin to /usr/bin it finds the updated python immediately. I then upgraded pip to the latest version and I appear to be good to go (though I am sure I shall find many other bumps in the road).
A very pleasant surprise was that the Mac knew about all my printers and was happy to try and use them for me. I won't know whether they work until I get back to the network to which they are connected, but if they do I will be both surprised and delighted. This is clearly superior technology where the user experience has been considered relatively carefully.
Unfortunately the user before me had already started using brew, so quite a lot of reowning was required to make my account the owner of essential locations before I could start to access the brew package again. Once I could start to think about doing that I discovered that brew update would not work because "The following untracked working tree files would be overwritten by merge". Thanks to this very helpful web page I updated by brew installation and then the update went ahead just fine. After which a brew upgrade decided that 35 packages needed updating (gulp!) and so I am currently waiting to see if the following packages upgrade without issues:
ack 2.10, atk 2.10.0, cairo 1.12.16, cmake 126.96.36.199, erlang R16B02, fontconfig 2.11.0, gdk-pixbuf 2.30.1, gettext 0.18.3.1, gfortran 4.8.2, git 188.8.131.52, glib 2.38.2, gmp 5.1.3, gtk+ 2.24.22, harfbuzz 0.9.24, icu4c 52.1, libmemcached 1.0.17, libxml2 2.9.1, mercurial 2.8, mplayer 1.1.1, ncdu 1.10, nmap 6.40, pango 1.36.1, pixman 0.32.2, postgresql 9.3.1, pv 1.4.6, pypy 2.2.0, python 2.7.6, python3 3.3.2, redis 2.6.16, sphinx 2.1.3, sqlite 3.8.1, xz 5.0.5, zeromq 3.2.4I'll let you know how it goes! In the meantime, though my virtual environments still need some attention I am able to run Pythons 2 and 3 and the IPython Notebook. Kudos to Apple, this migration has left me much happier than I would have imagined.