[issue4391] optparse: use proper gettext plurals forms

[David W. Lambert]

David W. Lambert <lambertdw at corning.com> added the comment:

And while at it, replace "usage" with "Use".
"Usage" isn't a word.

----------
nosy: +LambertDW

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue4391>
_______________________________________