URL: https://github.com/SSSD/sssd/pull/783 Author: branen Title: #783: knownhostsproxy: friendly error msg for NXDOMAIN Action: opened

PR body: """ This patch writes a brief, familiar error message to stderr when no addresses are able to be resolved for the host specified in argv:

``` (with patch)$ ssh the-void sss_ssh_knownhostsproxy: Could not resolve hostname the-void ssh_exchange_identification: Connection closed by remote host ```

Users accustomed to using SSH in environments where SSSD is not deployed may expect the usual "Could not resolve hostname" error from SSH when a domain name is misspelled or otherwise invalid:

``` (no sssd)$ ssh the-void ssh: Could not resolve hostname the-void: Name or service not known ```

When such users begin using SSH in an SSSD-enabled environment, they may be confused when this familiar and straightforward message is replaced by a new one:

``` (sssd)$ ssh the-void ssh_exchange_identification: Connection closed by remote host ```

If such users aren't aware that the system `ssh_config` is proxying their connection through `sss_ssh_knownhostsproxy`, they may mistakenly conclude that a connection had been made all the way to a remote host and, therefore, that the hostname they specified was valid and able to be resolved. This patch mitigates this opportunity for confusion. """

To pull the PR as Git branch: git remote add ghsssd https://github.com/SSSD/sssd git fetch ghsssd pull/783/head:pr783 git checkout pr783