[#3060] set ckan.locale_default as language for FormEncode

- If this is not done FormEncode takes the system LANG for its
  validation messages which might lead to unexpected behaviour.
- This also leads to the tests passing on machines where the LANG is
  set to something other then `en`
- More information can be found at
  http://www.formencode.org/en/latest/Validator.html#localization-of-error-messages-i18n

ckan/lib/navl/dictization_functions.py

@@ -6,6 +6,9 @@
 
 from ckan.common import _
 
+default_lang = config.get('ckan.locale_default', 'en')
+fe.api.set_stdtranslation(domain="FormEncode", languages=default_lang)
+
 class Missing(object):
     def __unicode__(self):
         raise Invalid(_('Missing value'))