Re-posting closed issue https://github.com/travis-ci/travis-ci/issues/10313 here, so that it has a chance of being fixed in the product and saving future users some hassle.
Steps to reproduce:
$ travis login --github-token pancakes
A login failure message should be printed to the console.
Command exits and no output is printed to the console.
As a new user of travis, I erroneously assumed that a lack of output implied that the login command worked.