fix(cron): expand _SCRIPT_FAILURE_PHRASES with SSH patterns

Part of #457, Closes #350

Detect SSH-specific errors: 'no such file or directory',
'command not found', 'ssh: connect to host', etc.

cron/scheduler.py

@@ -182,6 +182,15 @@ _SCRIPT_FAILURE_PHRASES = (
     "exit status",
     "non-zero exit",
     "did not complete",
+    # SSH-specific failure patterns (#350)
+    "no such file or directory",
+    "command not found",
+    "hermes binary not found",
+    "hermes not found",
+    "ssh: connect to host",
+    "connection timed out",
+    "host key verification failed",
+    "no route to host",
     "could not run",
     "unable to execute",
     "permission denied",