aenum: make tests pass (#33805)

For Python 2, tests were failing because they depended on a particular
way of executing the tests module as it defined a global variable
and created a temporary file. Running it through setup.py didn't work.
Invoking it directly solved the issue.

For Python 3, aenum tests were disabled, however, they did't have to
fail. Configuring UTF8 locale resolved the failure that was happening
after the above fix for Python 2 was applied.