Twig 1.21.2 has just been released and contains a fix for a bug that breaks a lot of applications including recent versions of Symfony (2.3 and 2.7 latest releases; 2.3.32 and 2.7.4).
Here is the full changelog:
- fixed variable names for the deprecation triggering code
 - fixed escaping strategy detection based on filename
 - added Traversable support for replace, merge, and sort
 - deprecated support for character by character replacement for the "replace" filter
 
Nice one!