Karma with Webpack 2 raises errors about Promises

[jambonrose]

Expected behavior

Karma+Webpack2 runs without raising errors about Promises (especially when none of the tests or code use Promises).

Actual behavior

Each time Karma fetches a file with the webpack preprocessor, it raises the following warning:

Fetching src/ExampleTest.js
Warning: .then() only accepts functions but was passed: [object Undefined], [object Undefined]
    at then (node_modules/karma/lib/middleware/common.js:14:39)
    at node_modules/karma/lib/middleware/source_files.js:29:25
    at call (node_modules/connect/index.js:239:7)
    at next (node_modules/connect/index.js:183:5)
    at node_modules/karma/lib/middleware/karma.js:231:12
    at call (node_modules/connect/index.js:239:7)
    at next (node_modules/connect/index.js:183:5)
    at node_modules/karma/lib/middleware/strip_host.js:13:5
    at call (node_modules/connect/index.js:239:7)
    at next (node_modules/connect/index.js:183:5)
    at node_modules/karma/lib/middleware/stopper.js:9:50
    at call (node_modules/connect/index.js:239:7)

Enviroment Details

Karma 1.1.0 with Webpack 2 through Babel 6 on macOS 10.11.5 with npm 3.8.8 and node v5.11.0. Please see package.json for full requirements.

Steps to reproduce the behaviour

1. Clone the example repo found at https://github.com/jambonsw/webpack2-karma-logging-error-mve
2. Install the packages with npm install
3. Run tests with npm test

[jambonrose]

Forgot to mention: you can also see this behavior in the example output in #2217.

[shaharmor]

Any update on this?