Exception handling for data outputs (#12797) (#12800)

(cherry picked from commit 4a0e28510f)

Co-authored-by: Oliver <oliver.henry.walters@gmail.com>

src/backend/InvenTree/report/tasks.py

@@ -32,10 +32,24 @@ def print_reports(
     try:
         template = ReportTemplate.objects.get(pk=template_id)
         output = DataOutput.objects.get(pk=output_id)
+    except DataOutput.DoesNotExist:
+        # The DataOutput may have already been consumed and deleted by the time
+        # this task runs (e.g. if the background worker redelivered the task)
+        logger.info(
+            'DataOutput %s no longer exists - skipping print_reports task', output_id
+        )
+        return
     except Exception:
         log_error('report.tasks.print_reports')
         return
 
+    if output.complete:
+        # This task has already been processed (e.g. a redelivered/duplicate task) - skip it
+        logger.info(
+            'DataOutput %s is already complete - skipping print_reports task', output_id
+        )
+        return
+
     # Fetch user information
     user = None
 
@@ -86,10 +100,24 @@ def print_labels(
     try:
         template = LabelTemplate.objects.get(pk=template_id)
         output = DataOutput.objects.get(pk=output_id)
+    except DataOutput.DoesNotExist:
+        # The DataOutput may have already been consumed and deleted by the time
+        # this task runs (e.g. if the background worker redelivered the task)
+        logger.info(
+            'DataOutput %s no longer exists - skipping print_labels task', output_id
+        )
+        return
     except Exception:
         log_error('report.tasks.print_labels')
         return
 
+    if output.complete:
+        # This task has already been processed (e.g. a redelivered/duplicate task) - skip it
+        logger.info(
+            'DataOutput %s is already complete - skipping print_labels task', output_id
+        )
+        return
+
     # Fetch user information
     user = None