Update psycopg2 to 2.7.7

[pyup-bot]

This PR updates psycopg2 from 2.7.6.1 to 2.7.7.

Changelog

2.7.7

^^^^^^^^^^^^^^^^^^^^^^^^^^^

- Cleanup of the cursor results assignment code, which might have solved
double free and inconsistencies in concurrent usage (:tickets:`346, 384`).
- Wheel package compiled against OpenSSL 1.0.2q.

Links

• PyPI: https://pypi.org/project/psycopg2
• Changelog: https://pyup.io/changelogs/psycopg2/
• Homepage: http://initd.org/psycopg/

[pyup-bot]

Closing this in favor of #63