Bump psycopg2 from 2.7.3.2 to 2.7.4
Bump psycopg2 from 2.7.3.2 to 2.7.4

Bumps [psycopg2](http://initd.org/psycopg/) from 2.7.3.2 to 2.7.4.
arxiv-vanity/arxiv-vanity,arxiv-vanity/arxiv-vanity,arxiv-vanity/arxiv-vanity,arxiv-vanity/arxiv-vanity