[Answered ]-Buildout, psycopg2, postgresql

You can do it, but you’ll have to make your own recipe to do that check. There’s no existing recipe that does what you want.

An alternative is to have two buildout configs. The main buildout.cfg assumes postgresql is available and doesn’t attempt to build it.

A second withpostgres.cfg could look like this:

[buildout]
parts +=
    postgre
    psycopg2

[postgres]
... your existing one ...

[psycopg2]
... your existing one ...

Users that need to build it from source can use the second configuration by calling bin/buildout -c withpostres.cfg.

Would that solve your issue?