add support for the %(here)s token when using logging.fileConfig in env.py

[sqlalchemy-bot]

Migrated issue, originally created by Michael Bayer (@zzzeek)

so that %(here)s can be in the logging config. this is basically a change to env.py.mako.

[ParthS007]

Hi @zzzeek , I want to work on this Issue. How should I proceed with this?

[zzzeek]

@mikeywaites can you provide a little guidance here