Running xgettext on argparse.py (of any currently supported Python 3.x) return following warning:

./Lib/argparse.py: warning: 'msgid' format string with unnamed arguments cannot be properly localized: The translator cannot reorder the arguments. Please consider using a format string with named arguments, and a mapping instead of a tuple for the arguments.

Same problem was already partially fixed here: https://bugs.python.org/issue10528. I guess that this occurrence was either missed or is new since.

It would be nice to have this backported to all supported releases but considering incompatibility worries in issue linked above, it may be fixed only in 3.8+ (which is still nice).