Running testsuite on a half-uploaded tor browser fails
When the testsuite is being run on a release directory where the sha256sums-unsigned-build.txt is present, but not all of the bundle have been uploaded yet, the testsuite fails with an error on the first bundle that it cannot download.
We should either check that all bundle are present before starting the tests, or start them but if a bundle cannot be downloaded retry it after 15 or 30 minutes.