[connection] eliminate ClientConnection leftovers
* in the documentation
* in the docstrings
* in code notations (e.g. clt_cnx -> cnx)
Related to #3837233.
From now, there should be just one ClientConnection left in repoapi.py.
Upstream Author:
%(author)s <%(author-email)s>
Copyright:
Copyright (c) %(year)s %(author)s.
%(author-web-site)s -- mailto:%(author-email)s