To sum up the behavior, the following table displays whether
modules are read from the current working directory for various
ways how the python scripts can be launched (unfixed/fixed version):

unfixed   fixed   run as
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
yes       no      python test.py
yes       no      python ./test.py
yes       no      python /tmp/396/test.py
yes       no      /bin/env python test.py

yes       yes     test.py
yes       yes     ./test.py
yes       yes     /tmp/396/test.py
yes       yes     /usr/bin/python test.py
yes       yes     /usr/bin/python ./test.py
yes       yes     /usr/bin/python /tmp/396/test.py

no        no      test-in-different-dir.py
no        no      ./bin/test-in-different-dir.py
no        no      python ./bin/test-in-different-dir.py