ipa-replica-conncheck: handle ssh not installed

When ipa-replica-conncheck is run but ssh is not installed, the tool exits
with a stack trace. Properly handle the error by raising an Exception in the
SshExec constructor, and catch the exception in order to ignore the error and
skip ssh test.

The tool will exit with the following output:
[...]
Check RPC connection to remote master
trying https://master.domain.com/ipa/session/json
Forwarding 'schema' to json server 'https://master.domain.com/ipa/session/json'
Retrying using SSH...
WARNING: ssh not installed, skipping ssh test

https://pagure.io/freeipa/issue/6935

Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>

install/tools/ipa-replica-conncheck

@@ -59,12 +59,11 @@ class SshExec(object):
         self.user = user
         self.addr = addr
         self.cmd = distutils.spawn.find_executable('ssh')
-
-    def __call__(self, command, verbose=False):
         # Bail if ssh is not installed
         if self.cmd is None:
-            root_logger.warning("WARNING: ssh not installed, skipping ssh test")
-            return ('', '', 0)
+            raise RuntimeError("ssh not installed")
+
+    def __call__(self, command, verbose=False):
 
         tmpf = tempfile.NamedTemporaryFile()
         cmd = [
@@ -596,7 +595,11 @@ def main():
 
                 # Ticket 5812 Always qualify requests for admin
                 user = principal
-                ssh = SshExec(user, options.master)
+                try:
+                    ssh = SshExec(user, options.master)
+                except RuntimeError as e:
+                    root_logger.warning("WARNING: %s, skipping ssh test" % e)
+                    return 0
 
                 root_logger.info("Check SSH connection to remote master")
                 result = ssh('echo OK', verbose=True)