How to correctly manage RUN_DEPENDS for python based ports ?

[Olivier Cochard-Labbé]

Hi,

I'm working on porting www/py-bottle-cork (an authenticate module for
www/py-bootle).

This module support lot's of backend like:
- MySQL, MariaDB, PostgreSQL using SQLAlchemy
- MongoDb
- SQLite
- Local JSON files for low-traffic web applications

For my needs I only use local JSON files.
Then the Makefile currently include 2 RUN_DEPENDS:
RUN_DEPENDS=
${PYTHON_PKGNAMEPREFIX}bottle>=0.12:${PORTSDIR}/www/py-bottle \

${PYTHON_PKGNAMEPREFIX}beaker>=1.6.4:${PORTSDIR}/www/py-beaker

But as soon as you want to use other backend you end up with error like "no
module named sqlite3".

Should I put "minimum" RUN_DEPENDS and let users manage by them-self all
missing deps or should I use OPTIONS ?

Thanks