florian@apollo13:~/test_python$ python3.4 -m unittest
.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK
florian@apollo13:~/test_python$ ls tests/
__init__.py  test_bla.py
florian@apollo13:~/test_python$ cat tests/test_bla.py 
from unittest import TestCase

class TestBla(TestCase):
    def test_bla(self):
        assert True

florian@apollo13:~/test_python$ rm tests/__init__.py 
florian@apollo13:~/test_python$ python3.4 -m unittest

----------------------------------------------------------------------
Ran 0 tests in 0.000s

OK
florian@apollo13:~/test_python$ python3.4 -c "import tests.test_bla"  # No error