So, I read a little more about shebang and python modules. Shebang is only for define which interpreter to use to execute a script. Shebang is not used to determine the file type.

In our case, we have only few scripts : centralreport.py, config.py and test.py. All other python files are libraries or modules. A libraries shouldn't be executed, but used in a program or a script.
On all Python projects I looked, only scripts with the "main" function have a shebang. All python modules have only the encoding descriptor.
You can look some libraries we use for CentralReport, for example : 
https://github.com/bbangert/routes
https://github.com/mitsuhiko/jinja2

And some forums/helps : 
http://stackoverflow.com/questions/9783482/should-python-library-modules-start-with-usr-bin-env-python
http://bytes.com/topic/python/answers/631215-shebang-hashbang-modules-not

By adding a shebang on modules files, you will be able to execute the script with a shell. And this is not good : only main scripts should be called.