Log Message:
py-psycopg2: updated to 2.7.4

What's new in psycopg 2.7.4
- Moving away from installing the wheel package by default.
  Packages installed from wheel raise a warning on import. Added package
  psycopg2-binary to install from wheel instead.
- Convert fields names into valid Python identifiers in
  ~psycopg2.extras.NamedTupleCursor.
- Fixed Solaris 10 support.
- cursor.mogrify() can be called on closed cursors.
- Fixed setting session characteristics in corner cases on autocommit
  connections.
- Fixed ~psycopg2.extras.MinTimeLoggingCursor on Python 3.
- Fixed parsing of array of points as floats.
- Fixed ~psycopg2.__libpq_version__ building with libpq >= 10.1.
- Fixed ~cursor.rowcount after ~cursor.executemany() with :sql:RETURNING
  statements.
- Fixed compatibility problem with pypy3.
- Wheel packages compiled against PostgreSQL 10.1 libpq and OpenSSL 1.0.2n.
- Wheel packages for Python 2.6 no more available (support dropped from
  wheel building infrastructure).