Proposed changes

In order to get the unit tests running successfully on #3717, we need the download tests to have more disk space available. They are currently failing since they require the disk to have at least 5% free disk space in order for them to start a download.

These changes change the directory for the temporary files in the unit tests to be a subdirectory of /mnt, which is a separate disk on the github actions runner. This should mean that the tests don't fail due to InsufficientSpace in tedge_downloader_ext and therefore #3717 can be merged.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Improvement (general improvements like code refactoring that doesn't explicitly fix a bug or add any new functionality)
• Documentation Update (if none of the other choices apply)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Paste Link to the issue

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA (in all commits with git commit -s. You can activate automatic signing by running just prepare-dev once)
• I ran just format as mentioned in CODING_GUIDELINES
• I used just check as mentioned in CODING_GUIDELINES
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments