I received the following error while working on a Debian sid box:

$ schroot -l
terminate called after throwing an instance of 'std::runtime_error'
  what():  locale::facet::_S_create_c_locale name not valid
Aborted

With debconf + locales already installed, I ran ‘export | grep LANG’ to discover that my locale was set to ‘en_US.UTF-8’. Then I ran ‘dpkg-reconfigure locale’ and checked that locale and set it to the default.