The current version of Karma that we are using as our JS test framework can only redirect the browser log to the console, where it gets mixed in with the test result output.
Because of this we have turned off outputting of the browser log, despite it being helpful when there is an error. See
However the new version of Karma has introduced another config option, browserConsoleLogOptions, where we can define the path to the file for browser log. See the discussion at https://github.com/edx/edx-platform/pull/12710#discussion_r66691479
upgrade the version of Karma that we are using
redirect the browser console log to a file
make jenkins job configuration changes if needed to save that log as an artifact