Code review comment for lp:~mabac/linaro-image-tools/snowball-support

Yeah, we should have some unit tests for get_file_info(), create_toc() and install_snowball_boot_loader() as they're not tested even indirectly. But we also need to change test_snowball_image_steps to mock those 3 functions (now methods) using the same logger double that the testcase class uses to mock the other module-level functions.