Prefer binary package in setup.cfg

Question

My project (https://github.com/locustio/locust) depends on greenlet, but whenever there is a new release of that, there is a brief period when no binary version is available, and many of my users have issues with installing from source.

Is there a way to prefer an older binary version instead of the latest and greatest source version? E.g. prefer 2.0.1 that has a binary version over 2.0.2 that doesn't (or at least didn't at the time)

Considered alternate solutions:

• Set --prefer-binary from the pip command line, but it is somewhat hard to explain that to people.
• I could just lock it to 2.0.1, but that is overly rigid.