Ensure that _external_ids keys are strings

We had a lot of `Failed to find external id for job_id` messages on
rockfish, and I think that might have been part of the issue.

pulsar/managers/base/external.py

@@ -1,5 +1,9 @@
 import logging
 from string import Template
+from typing import (
+    Dict,
+    Any,
+)
 
 from pulsar.managers import status
 from .directory import DirectoryBaseManager
@@ -18,7 +22,7 @@ class ExternalBaseManager(DirectoryBaseManager):
 
     def __init__(self, name, app, **kwds):
         super().__init__(name, app, **kwds)
-        self._external_ids = {}
+        self._external_ids: Dict[str, Any] = {}
         self.job_name_template = kwds.get('job_name_template', DEFAULT_JOB_NAME_TEMPLATE)
 
     def clean(self, job_id):
@@ -46,11 +50,11 @@ def _register_external_id(self, job_id, external_id):
         if isinstance(external_id, bytes):
             external_id = external_id.decode("utf-8")
         self._job_directory(job_id).store_metadata(JOB_FILE_EXTERNAL_ID, external_id)
-        self._external_ids[job_id] = external_id
+        self._external_ids[str(job_id)] = external_id
         return external_id
 
     def _external_id(self, job_id):
-        return self._external_ids.get(job_id, None)
+        return self._external_ids.get(str(job_id), None)
 
     def _job_name(self, job_id):
         env = self._job_template_env(job_id)
@@ -59,9 +63,9 @@ def _job_name(self, job_id):
     def _recover_active_job(self, job_id):
         external_id = self._job_directory(job_id).load_metadata(JOB_FILE_EXTERNAL_ID, FAILED_TO_LOAD_EXTERNAL_ID)
         if external_id and external_id is not FAILED_TO_LOAD_EXTERNAL_ID:
-            self._external_ids[job_id] = external_id
+            self._external_ids[str(job_id)] = external_id
         else:
             raise Exception("Could not determine external ID for job_id [%s]" % job_id)
 
     def _deactivate_job(self, job_id):
-        del self._external_ids[job_id]
+        del self._external_ids[str(job_id)]