warn and exit if ssh-import-id not available

cloudinit/config/cc_ssh_import_id.py

@@ -35,12 +35,19 @@
 from cloudinit import subp, util
 from cloudinit.distros import ug_util
 
+SSH_IMPORT_ID = "ssh-import-id"
+
 # https://launchpad.net/ssh-import-id
 distros = ["ubuntu", "debian"]
 
 
 def handle(_name, cfg, cloud, log, args):
-
+    if cfg.get('ssh_import_id') and subp.which(SSH_IMPORT_ID):
+        log.warn(
+            "ssh-import-id is not installed, but module ssh_import_id is "
+            "configured. Skipping module."
+        )
+        return
     # import for "user: XXXXX"
     if len(args) != 0:
         user = args[0]
@@ -100,7 +107,7 @@ def import_ssh_ids(ids, user, log):
     except KeyError as exc:
         raise exc
 
-    cmd = ["sudo", "-Hu", user, "ssh-import-id"] + ids
+    cmd = ["sudo", "-Hu", user, SSH_IMPORT_ID] + ids
     log.debug("Importing SSH ids for user %s.", user)
 
     try: