We were importing _argparse (private) from cliff to get at
argparse.HelpFormatter, which was present there only because it was
being transitively imported directly from argparse itself. Commit
584352dcd008d58c433136539b22a6ae9d6c45cc got rid of this transitive
import, which means that rsdclient would have broken on the next cliff
release.
This commit just imports argparse directly instead.
And because that was the only reference to cliff in the project, this
commit also removes it from the requirements.
For more information, see http://lists.openstack.org/pipermail/openstack-discuss/2020-January/011852.html
Change-Id: I7f99d80a3be38acc45af83e54b32ebc2f5b40859
d1a515eac0