Bump psycopg2 from 2.6.1 to 2.8.6

Bumps [psycopg2](https://github.com/psycopg/psycopg2) from 2.6.1 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] <support@dependabot.com>

requirements.txt

@@ -11,6 +11,6 @@ django-toolbelt==0.0.1
 drfdocs==0.0.9
 gunicorn==19.4.5
 Pillow==3.2.0
-psycopg2==2.6.1
+psycopg2==2.8.6
 python-social-auth==0.2.19
 whitenoise==2.0.3