debug tests behind EDL - failing builds for PRs to main

[rwegener2]

PR #447 is an example of a build that ran well with merges to development or release, but the build fails due to an authentication error when merging to main. This was an issue for the release of both 0.7.0 and 0.8.0, after the integration of earthaccess.

The main branch is failing because:

because the behind_NSIDC_login test suite is only run on the main branch (so in the list of checks, the "branch" test run passes, but when the additional tests are triggered for the "pull request" (what the merged code will look like) it fails).
(From @JessicaS11 in #447)

[JessicaS11]

Per the .travis.yml setup, including the string nsidc_tests in the commit message should trigger the test_behind_earthdata_login tests.