Merge pull request #5983 from cylc/8.2.x-sync

🤖 Merge 8.2.x-sync into master

Author: oliver-sanders

cylc/flow/job_runner_handlers/documentation.py

@@ -421,6 +421,14 @@ def submit(
         Returns:
             (ret_code, out, err)
 
+            ret_code:
+                Subprocess return code.
+            out:
+                Subprocess standard output, note this should be newline
+                terminated.
+            err:
+                Subprocess standard error.
+
         """
         raise NotImplementedError()