Exporting CSV file that contains Unicode text fails on Python 3 on Windows
### Observed behavior
User reports of CSV file export failing prompted me to add a test for this in a Windows environment in https://github.com/learningequality/kolibri/pull/7899.

When Unicode text should be inserted into the exported CSV, such as a Unicode username or full_name, then an error occurs on windows.

```
Error trying to write csv file: 'charmap' codec can't encode characters in position 29-35: character maps to <undefined>
```

### Expected behavior
CSV Export should work on all platforms.

This is fixed by this commit: https://github.com/learningequality/kolibri/pull/7899/commits/c088d08b3e6c4a0f4194a17062457cbd7ae34816

### User-facing consequences
Windows users are unable to export CSV files.

diff --git a/kolibri/core/logger/csv_export.py b/kolibri/core/logger/csv_export.py
index 0e2ff6c9ff..6526e9ae2b 100644
--- a/kolibri/core/logger/csv_export.py
+++ b/kolibri/core/logger/csv_export.py
@@ -154,7 +154,7 @@ def csv_file_generator(facility, log_type, filepath, overwrite=False):
     if sys.version_info[0] < 3:
         csv_file = io.open(filepath, "wb")
     else:
-        csv_file = io.open(filepath, "w", newline="")
+        csv_file = io.open(filepath, "w", newline="", encoding="utf-8")
 
     with csv_file as f:
         writer = csv.DictWriter(f, header_labels)
['kolibri/core/logger/csv_export.py']