[sagecell] ssh(): start ssh-egent and adds keys in one "local()" function
[sagecell] ssh(): start ssh-egent and adds keys in one "local()" function

sagecell/sagecell.py: change ssh(). Ensure ssh-agent is enabled and
adds private key identities to the authentication agent
in one "local()" function

korniichuk/sagecell,korniichuk/sagecell