ios Swift 4 installing PromiseKit json parse error

Question

I add this line

pod "PromiseKit", "~> 6.0"

to my Podfile and hit pod update, only to get below error:

JSON::ParserError - 416: unexpected token at '{
  "name": "QuartzCore",
  "tvos": {
    "source_files": "Extensions/QuartzCore/Sources/*",
    "frameworks": "QuartzCore"
  },
  "ios": {
    "source_files": "Extensions/QuartzCore/Sources/*",
    "frameworks": "QuartzCore"
  },
  "osx": {
    "source_files": "Extensions/QuartzCore/Sources/*",
    "frameworks": "QuartzCore"
  },
  "dependencies": {
    "PromiseKit/CorePromise": [

    ]
  },
  "platforms": {
    "ios": "8.0",
    "osx": "10.1'

Tried different version but not able to install PromiseKit.