When performing on Travis-CI, Gradle thinks that the terminal is an ANSI one and thus try to use features non available to the Travis log window:
  • deletion of characrters
  • coloring
  • ...
Thus the build log is ugly and even going into the "plain text" version of the log shows strange non printable charcaters.

In order to resolve this, you can change the TERM variable by adding in your .travis.yml file:
before_install:
  - "export TERM=dumb"