Coverage information is not being added to MRs

Currently coverage information is not being uploaded meaning that we don't get coverage information on MR diffs. This is because we're writing coverage to, /builds/uis/devops/iam/activate-account/api/tox-artifacts/coverage.xml but expect to find it at .../tox-artifacts/py3/coverage.xml.

This might indicate a boilerplate bug and, if so, we should open an issue to fix the boilerplate once this is fixed.

Extract from representative CI log

py3: commands[3]> coverage xml -o /builds/uis/devops/iam/activate-account/api/tox-artifacts/coverage.xml
Wrote XML report to /builds/uis/devops/iam/activate-account/api/tox-artifacts/coverage.xml
  py3: OK (30.43=setup[2.03]+cmd[15.67,11.51,0.51,0.36,0.36] seconds)
  congratulations :) (30.59 seconds)
Uploading artifacts for successful job 00:02
Uploading artifacts...
/builds/uis/devops/iam/activate-account/api/tox-artifacts/: found 48 matching artifact files and directories 
Uploading artifacts as "archive" to coordinator... 201 Created  id=1800653 responseStatus=201 Created token=glcbt-64
Uploading artifacts...
WARNING: /builds/uis/devops/iam/activate-account/api/tox-artifacts/py3/junit.xml: no matching files. Ensure that the artifact path is relative to the working directory (/builds/uis/devops/iam/activate-account/api) 
ERROR: No files to upload                          
Uploading artifacts...
WARNING: /builds/uis/devops/iam/activate-account/api/tox-artifacts/py3/coverage.xml: no matching files. Ensure that the artifact path is relative to the working directory (/builds/uis/devops/iam/activate-account/api)