Hi! travis-ci build is busted with Crystal 0.27.1.
Installing Crystal OK Reading package lists... Building dependency tree... Reading state information... libgmp-dev is already the newest version (2:5.1.3+dfsg-1ubuntu1). libgmp-dev set to manually installed. The following additional packages will be installed: libevent-core-2.0-5 libevent-dev libevent-extra-2.0-5 libevent-openssl-2.0-5 libevent-pthreads-2.0-5 The following NEW packages will be installed: crystal libevent-core-2.0-5 libevent-dev libevent-extra-2.0-5 libevent-openssl-2.0-5 libevent-pthreads-2.0-5 0 upgraded, 6 newly installed, 0 to remove and 288 not upgraded. Need to get 40.2 MB of archives. After this operation, 185 MB of additional disk space will be used. WARNING: The following packages cannot be authenticated! crystal E: There were unauthenticated packages and -y was used without --allow-unauthenticated