[repository,tests] use the new connection api (part 1/2) `add_info` should not play with the cnxset nor the mode. Static analysis showed that: * add_info is an internal api called with a non-none cnx.cnxset and also in write mode * only the altered test violated this assumption, which is now somewhat documented

from os.path import join
assert __file__.endswith(join('scripts', 'script3.py')), __file__
assert '__main__' == __name__, __name__
assert ['-vd', '-f', 'FILE.TXT'] == __args__, __args__