Fix intermittent failures of integration tests

[zschira]

This CI run contains an error that seems to be occurring intermittently. It happens in the tests/integration/zenodo_test.py when trying to download files to verify contents after an archiver run. Sometimes when doing so, the file we get is empty causing the test to fail. This might just be a case where we need to add retries to the downloads in the test, but this needs further investigation.