Space migration failing with "Export file is not a file" while migrating with CCMA

Issue Summary

The space migration is failing while migrating from Server/DC to Cloud.

Steps to Reproduce

1. Migrate multiple spaces from Confluence server to Cloud.
2. A few spaces are failing to migrate with the following error:

   "An unexpected error occurred during step: Uploading data. Error: Export file is not a file."

Expected Results

All spaces should migrate without any failures.

Actual Results

The below exception is thrown:

"An unexpected error occurred during step: Uploading data. Error: Export file is not a file."

Workaround

Retry those spaces and they will migrate successfully.