Memory leak

Hi,

For some obscure reason, the test bob.io.video.test.test_memory_leak fails on the macpro https://gitlab.idiap.ch/bob/bob.io.video/-/jobs/161805 , but not on the macmini https://gitlab.idiap.ch/bob/bob.io.video/-/jobs/161809

This is blocking the nightlies https://gitlab.idiap.ch/bob/bob.nightlies/-/jobs/161781

Tiago