Issue
When building an app with psycopg2 as a dependency, you receive the error Error: could not determine PostgreSQL version from '10.x' in the build output when building the dependency.
Resolution
psycopg2 versions below 2.7 are incompatible with the version of libpq-dev used in the stack images on Heroku, as the pg_config utility returns a version format that cannot be parsed by earlier psycopg2 versions. To resolve this issue, you will need to upgrade psycopg2 to 2.7 and up.