It looks like wikilabels-test requires a password for sudo-ing. This is new. I'm not sure what is up. This has happened in the past and @yuvipanda or @madhuvishy had taken care of it.
$ fab stage [wikilabels-test.eqiad.wmflabs] Executing task 'stage' [wikilabels-test.eqiad.wmflabs] sudo: git fetch origin [wikilabels-test.eqiad.wmflabs] out: [wikilabels-test.eqiad.wmflabs] out: We trust you have received the usual lecture from the local System [wikilabels-test.eqiad.wmflabs] out: Administrator. It usually boils down to these three things: [wikilabels-test.eqiad.wmflabs] out: [wikilabels-test.eqiad.wmflabs] out: #1) Respect the privacy of others. [wikilabels-test.eqiad.wmflabs] out: #2) Think before you type. [wikilabels-test.eqiad.wmflabs] out: #3) With great power comes great responsibility. [wikilabels-test.eqiad.wmflabs] out: [wikilabels-test.eqiad.wmflabs] out: sudo password: