Bump psycopg2-binary from 2.7.7 to 2.8.6

Bumps [psycopg2-binary](https://github.com/psycopg/psycopg2) from 2.7.7 to 2.8.6.
- [Release notes](https://github.com/psycopg/psycopg2/releases)
- [Changelog](https://github.com/psycopg/psycopg2/blob/master/NEWS)
- [Commits](https://github.com/psycopg/psycopg2/commits)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

requirements.txt

@@ -8,7 +8,7 @@ eventbrite==3.3.3
 gunicorn==19.9.0
 idna==2.8
 opbeat==3.5.2
-psycopg2-binary==2.7.7
+psycopg2-binary==2.8.6
 pytz==2018.9
 requests==2.21.0
 urllib3==1.24.2