improved the reporting of assertion failures for unicode characters
improved the reporting of assertion failures for unicode characters

basically, instead of throwing an 'unprintable AssertionError' object,
the error message report exactly which character it failed to interpret
for a given console's character encoding

peterayeni/rapidsms,rapidsms/rapidsms-core-dev,unicefuganda/edtrac,catalpainternational/rapidsms,ehealthafrica-ci/rapidsms,ken-muturi/rapidsms,catalpainternational/rapidsms,caktus/rapidsms,peterayeni/rapidsms,unicefuganda/edtrac,lsgunth/rapidsms,catalpainternational/rapidsms,eHealthAfrica/rapidsms,lsgunth/rapidsms,ehealthafrica-ci/rapidsms,peterayeni/rapidsms,eHealthAfrica/rapidsms,caktus/rapidsms,ehealthafrica-ci/rapidsms,ken-muturi/rapidsms,unicefuganda/edtrac,dimagi/rapidsms-core-dev,eHealthAfrica/rapidsms,lsgunth/rapidsms,ken-muturi/rapidsms,peterayeni/rapidsms,dimagi/rapidsms,catalpainternational/rapidsms,dimagi/rapidsms-core-dev,caktus/rapidsms,lsgunth/rapidsms,rapidsms/rapidsms-core-dev,dimagi/rapidsms