Comment 2 for bug 1349491

Here's a proposed patch for the issue. It also applies cleanly on icehouse (where I was able to reproduce the problem), I'll provide a havana version later on.

It's the second time we get bitten by the way we use filters in python files (cf. bug 1320235), after a solution for this gets merged I'll look into refactoring the solutions so they're more reusable. Maybe in a horizon/tables/filters.py file for filters known to be problematic, or introspecting for an autoescape argument so that might be too costly performance-wise...