We suspect this appearing now is due to a change in some gem. Here is a diff of 'gem list' on my dev box (where the old template code works) and our new box that broke today.

2,7c2,7
< actionmailer (3.0.15, 3.0.14, 3.0.10)
< actionpack (3.0.15, 3.0.14, 3.0.10)
< activemodel (3.2.6, 3.0.15, 3.0.14, 3.0.10, 3.0.9)
< activerecord (3.2.6, 3.0.15, 3.0.14, 3.0.10, 3.0.9)
< activeresource (3.0.15, 3.0.14, 3.0.10)
< activesupport (3.2.6, 3.0.15, 3.0.14, 3.0.10, 3.0.9)
---
> actionmailer (3.0.17)
> actionpack (3.0.17)
> activemodel (3.0.17)
> activerecord (3.0.17)
> activeresource (3.0.17)
> activesupport (3.0.17)
10c10,11
< arel (3.0.2, 2.0.10)
---
> apipie-rails (0.0.9)
> arel (2.0.10)
13,17c14,16
< awesome_print (1.0.2)
< builder (3.0.0, 2.1.2)
< bundler (1.1.5, 1.0.15)
< columnize (0.3.6)
< daemon_controller (0.2.6)
---
> builder (2.1.2)
> bundler (1.0.15)
> daemon_controller (1.0.0)
19c18
< excon (0.14.3, 0.14.2, 0.14.1, 0.13.4)
---
> excon (0.14.0)
21,22c20,22
< fog (1.4.0)
< formatador (0.2.3, 0.2.1)
---
> fog (1.6.0)
> foremancli (1.0)
> formatador (0.2.1)
24,26c24
< hirb (0.7.0, 0.6.2)
< hirb-unicode (0.0.5)
< i18n (0.6.0, 0.5.0)
---
> i18n (0.5.0)
28,37c26,29
< jruby-pageant (1.0.2)
< json (1.7.3, 1.6.6)
< linecache (0.46)
< mail (2.3.3, 2.2.19)
< metaclass (0.0.1)
< mime-types (1.19, 1.18)
< mocha (0.12.0, 0.11.4)
< multi_json (1.3.6, 1.3.5)
< mysql (2.8.1)
< mysql2 (0.3.11, 0.2.18)
---
> json (1.6.6)
> mail (2.3.3)
> mime-types (1.18)
> multi_json (1.2.0)
41,43c33,36
< net-ssh (2.5.2, 2.5.1, 2.3.0)
< nokogiri (1.5.5, 1.5.4, 1.5.2)
< passenger (3.0.12)
---
> net-ssh (2.3.0)
> nokogiri (1.5.2)
> oauth (0.4.6)
> passenger (3.0.17)
45,46c38,40
< puppet-module (0.3.4)
< rack (1.2.5)
---
> puppet-lint (0.3.1)
> rabl (0.7.0)
> rack (1.4.1, 1.2.5)
49,54c43,45
< rails (3.0.15, 3.0.14, 3.0.10)
< railties (3.0.15, 3.0.14, 3.0.10)
< rake (0.9.2.2, 0.8.7)
< rbovirt (0.0.12)
< rbvmomi (1.5.1)
< rbx-require-relative (0.0.9)
---
> rails (3.0.17)
> railties (3.0.17)
> rake (0.9.2.2)
55a47
> redcarpet (2.1.1)
57,59d48
< rr (1.0.4)
< ruby-debug (0.10.4)
< ruby-debug-base (0.10.4)
64,68c53,54
< scoped_search (2.3.7, 2.3.6)
< sexp_processor (3.2.0, 3.1.0)
< shoulda (3.1.1, 3.0.1)
< shoulda-context (1.0.0)
< shoulda-matchers (1.2.0, 1.0.0)
---
> scoped_search (2.3.7)
> sexp_processor (3.1.0)
70c56
< sqlite3 (1.3.6)
---
> sqlite3-ruby (1.2.4)
73,76c59,60
< trollop (1.16.2)
< tzinfo (0.3.33, 0.3.32)
< unicode-display_width (0.1.1)
< uuidtools (2.1.3, 2.1.2)
---
> tzinfo (0.3.32)
> uuidtools (2.1.1)
78d61
< wirb (0.4.2)

Pull request is https://github.com/theforeman/foreman/pull/171