[cleanup] show a FutureWarning for deprecation warnings in i18n.py
[cleanup] show a FutureWarning for deprecation warnings in i18n.py

show a FutureWarning with 5 years old
issue_deprecation_warning in i18n.py

Change-Id: I3f0018543a549c3dc952eb5da74de78ba12de4d2

wikimedia/pywikibot-core,wikimedia/pywikibot-core