Closed #23365 -- Makemigrations allows timezone-aware datetimes

When a user is adding a new, non-nullable datetime field to their model, 
they're now able to use django util's timezone module to supply a 
timezone-aware value. The prompt also shows an example using the 
preferred timezone.now() instead of datetime's naive now().
This should help: http://hg.python.org/cpython/file/5bc23c111de1/Lib/datetime.py#l1570