Pytest compatibility

When we use pytest to test our packages, some tests do not run because they are not found by pytest. Pytest ignores test.py files and does not consider them tests! Looking at the checkout of some bob packages that I have, these packages have a test.py file:

../bob.pad.base/bob/pad/base/test/test.py
../bob.db.mnist/bob/db/mnist/test.py
../bob.io.image/bob/io/image/test.py
../bob.db.atnt/bob/db/atnt/test.py
../bob.bio.vein/bob/bio/vein/tests/test.py
../bob.blitz/bob/blitz/examples/bob.example.extension/bob/example/extension/test.py                         
../bob.blitz/bob/blitz/examples/bob.example.library/bob/example/library/test.py                             
../bob.blitz/bob/blitz/examples/bob.example.project/bob/example/project/test.py                             
../bob.blitz/bob/blitz/test.py
../bob.devtools/bob/devtools/scripts/test.py
../bob.learn.activation/bob/learn/activation/test.py
../bob.io.stream/bob/io/stream/test/test.py
../bob.ip.stereo/bob/ip/stereo/test/test.py
../bob.io.audio/bob/io/audio/test.py
../bob.io.video/bob/io/video/test.py
../bob.ip.color/bob/ip/color/test.py
../bob.ip.facedetect/bob/ip/flandmark/test.py
../bob.ip.gabor/bob/ip/gabor/test.py
../bob.ip.qualitymeasure/bob/ip/qualitymeasure/test.py                                                      
../bob.learn.linear/bob/learn/linear/test.py
../bob.learn.pytorch/bob/learn/pytorch/test/test.py