Log Message:
Updated py-psycopg2 to 2.7.1.

What's new in psycopg 2.7.1
^^^^^^^^^^^^^^^^^^^^^^^^^^^

- Ignore `!None` arguments passed to `~psycopg2.connect()` and
  `~psycopg2.extensions.make_dsn()` (:ticket:`#517`).
- OpenSSL upgraded from major version 0.9.8 to 1.0.2 in the Linux wheel
  packages (:ticket:`#518`).
- Fixed build with libpq versions < 9.3 (:ticket:`#520`).