Updating Karma to v5+ : PromiseContainer is not a constructor

[guiann]

Hello,

We are using karma-iframes for a while, with Karma v4.4.1

When trying to upgrade to Karma v5+ (tried several v5+ with no more success)
karma-server refuse to start with this error :

31 08 2020 11:30:29.879:ERROR [karma-server]: Server start failed on port 9877: TypeError: common.PromiseContainer is not a constructor npm ERR! code ELIFECYCLE npm ERR! errno 130

This doesn't occur if I remove "iframes" from our list of frameworks.

Is there a needed configuration change for karma-iframes when upgrading karma from v4 to v5 ?

Thanks for the help.

Edit:
here is our dev dependencies for karma plugins :

    "karma": "5.1.1",
    "karma-chrome-launcher": "^2.2.0",
    "karma-coverage-istanbul-reporter": "^2.0.4",
    "karma-iframes": "^1.2.2",
    "karma-junit-reporter": "^1.2.0",
    "karma-mocha": "^2.0.1",
    "karma-sinon-chai": "^2.0.2",
    "karma-sourcemap-loader": "^0.3.8",
    "karma-spec-reporter": "0.0.32",
    "karma-webpack": "^4.0.2",

relevant configuration :

  config.set({
    frameworks: ["mocha", "sinon-chai", "iframes"],
    reporters: ["spec", "coverage-istanbul", "junit"],
    files: [
      'test/**/*.spec.js'
    ],
    preprocessors: {
      'test/**/*.spec.js': ["webpack", "sourcemap", "iframes"]
    },