Improve remote sync error handling

pydatalab/pydatalab/remote_filesystems.py

@@ -208,7 +208,16 @@ def _call_remote_tree(
         except Exception as exc:
             raise RuntimeError(f"Remote tree process {command!r} returned: {exc!r}")
         if stderr:
-            raise RuntimeError(f"Remote tree process {command!r} returned: {stderr!r}")
+            # Do not return the bare stderr, but instead specialise the error message to common errors
+            if "WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!" in stderr.decode("utf-8"):
+                msg = f"Remote host identification has changed for {hostname}: please contact the administrator of this datalab deployment."
+                LOGGER.error(
+                    "Remote host identification for %s has changed, failed to update remote directories",
+                    hostname,
+                )
+            else:
+                msg = "Remote tree process returned an error: please contact the administrator of this datalab deployment."
+            raise RuntimeError(msg)
 
         try:
             return json.loads(stdout)