module I18n

def self.reserve_key(key)

before any I18n.translate (etc) calls are made.
extra keys as I18n options, you should call I18n.reserve_key
and can't also be used for interpolation. If you are using any
Marks a key as reserved. Reserved keys are used internally, 
def self.reserve_key(key)
  RESERVED_KEYS << key.to_sym
  @reserved_keys_pattern = nil
end