JSON::ParserError: 822: unexpected token at 'OK'

https://sentry.gitlab.net/gitlab/gitlabcom/issues/440670/

JSON::ParserError: 822: unexpected token at 'OK'
  json/common.rb:155:in `parse'
    Parser.new(source, opts).parse
  json/common.rb:155:in `parse'
    Parser.new(source, opts).parse
  httparty/parser.rb:118:in `json'
    JSON.parse(body, :quirks_mode => true, :allow_nan => true)
  httparty/parser.rb:138:in `parse_supported_format'
    send(format)
  httparty/parser.rb:105:in `parse'
    parse_supported_format
...
(45 additional frame(s) were not displayed)

822: unexpected token at 'OK'