Install script fails

[andrewphilipsmith]

How to recreate:
run per-user-esri-addin-install.py

Expected result:
The scrip either installs the available addins, or registers to run via Start menu -> Startup as appropriate.

Actual result:

Traceback (most recent call last):
  File "..........\per-user-esri-addin-install.py", line 111, in <module>
    remove_old_addin(regaddinexe, old_addin_uids)
NameError: name 'remove_old_addin' is not defined

The method remove_old_addin does not exist in this file.