BUG #9168: Invalid JSON output generated by SQL statement

The following bug has been logged on the website:

Bug reference:      9168
Logged by:          Gary Teh
Email address:      garyjob@krake.io
PostgreSQL version: 9.2.2
Operating system:   MacOS X 10.7.5
Description:

Statement to create the database table
===
CREATE TABLE test_tables (
    properties hstore,
    "pingedAt" timestamp with time zone,
    id integer NOT NULL,
    "createdAt" timestamp with time zone NOT NULL,
    "updatedAt" timestamp with time zone NOT NULL
);

Statement to create a record
===
INSERT INTO
"test_tables"
("createdAt","updatedAt","pingedAt","properties") VALUES
('2014-2-10 0:10:28','2014-2-10 0:10:28','2014-2-10 0:10:28','"drug bank" =>
"cache \"that stuff"')

Statement to export the record into a JSON file
===
Copy (
  select
    array_to_json(
      array_agg( row_to_json(row)
    )
  )
  from (
    SELECT
      properties::hstore->'drug bank' as "drug bank",
      "pingedAt"
    FROM
      "test_tables"
    WHERE true
  ) row
) To '/tmp/invalid_json_output'

The invalid JSON output
[{
  "drug bank":"cache \\"that stuff",
  "pingedAt":"2014-02-09 16:10:28-08"
},{
  "drug bank":"cache \\"that stuff",
  "pingedAt":"2014-02-10 00:10:28-08"
}]

The final JSON output is not valid.