Fix: Bug fix MySQLdb

[BLasan]

Description UserManager.py and DownloadManager.py contained MySQLdb module member errors.

Related Issue Fix #902

Motivation and Context There should not be any bugs within the code. When running the exception part it may cause an error.

How Has This Been Tested? Open the UserManager.py and DownloadaManager.py files. Problems will be underlined with red lines.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed.