4.4 to 4.5.3 upgrade error

[KiltsRock.com]

running the auto-upgrade and get the following error on the login screen of the update.

Error: Undefined constant 'IPS\TEST_DELTA_TEMPLATE_CHANGES' (0)

I've no idea what is going on.  Ideas?

[bfarber]

I did a full project search and we don't reference that constant anywhere in our code base. It looks like this might be related to a third party customization you have installed.