The generated file was completely unusable by the system
therefore the fix which ensures that diffing the file
prior to changes and after only shows diffs
Furthermore the code did not work for Python 3.6
> f.writelines(to_bytes(lines, errors='surrogate_or_strict'))
E TypeError: a bytes-like object is required, not 'int'
The other modifications (lambda variable renaming) is to
comply with default flake8 rules
* Added new module interfaces_file
* interfaces_file: added unit tests
* interfaces_file: added golden files for unit tests
* interfaces_file: moved to system modules
* interfaces_file: fixed code formatting and convention issues
