Force unicode literals for Python 2 compatibility of string handling.

[rtibbles]

Summary

• In 95609c1 we started doing string handling in the core CSV utils module
• We had not imported unicode literals into that module
• This seems to have caused issues with string handling in Python 2.7 where this is necessary
• This rectifies that
• This was not the issue ^
• Rather the unification of output_mapper functions between the three places it was used meant that there was a conditional in the combined output mapper that was not in the original log export one.
• This removes that conditional, and updates the demographic exclusion code for user exports to compensate.

References

Fixes #9601

Reviewer guidance

Run Kolibri in Python 2.7
Export session or summary logs
Check if resource and channel titles are present

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Testing checklist

• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included
• Critical user journeys are covered by Gherkin stories
• Critical and brittle code paths are covered by unit tests

PR process

• PR has the correct target branch and milestone
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• If this is an important user-facing change, PR or related issue has a 'changelog' label
• If this includes an internal dependency change, a link to the diff is provided

Reviewer checklist

• Automated test coverage is satisfactory
• PR is fully functional
• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md

[radinamatic]

Channel name and Content title columns are now populated correctly in the CSV logs 💯

Tested with DEB asset in Ubuntu 18.04.

[radinamatic]

Importing & exporting CSV with users also works as it's supposed to do, good to go!!! 👍🏽