Set dependabot python version to 2.7.17

[fdrozdowski]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Build was run locally and any changes were pushed
• Lint has passed locally and any fixes were made for failures

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):
  Automated dependency updates.

What is the current behavior?

When dependabot scans the repository, it will try to upgrade dependencies to the newest version, some of which might not be compatible with Python 2.7. This will result in PRs that we won't be able to merge because unit tests will likely fail.

What is the new behavior?

We will tell dependabot to only upgrade dependencies to the newest versions compatible with Python 2.7.17. For examples of automated dependabot PRs, please see: https://github.com/fdrozdowski/virtualization-sdk/pulls.

Does this introduce a breaking change?

• Yes
• No

Other information