• Use a meaningful title for the pull request. Include the name of the package modified.
• Test the change in your own code. (Compile and run.)
• Follow the advice from the readme.
• Avoid common mistakes.
• Run npm run lint package-name (or tsc if no tslint.json is present).
• Provide a URL to documentation or source code which provides context for the suggested changes: https://github.com/webpack/webpack-dev-middleware/blob/master/breaking-changes.md
• Increase the version number in the header if appropriate.
• If you are making substantial changes, consider adding a tslint.json containing { "extends": "dtslint/dt.json" }.

Got following build error:

Error in karma-webpack
Command failed: node /home/travis/build/DefinitelyTyped/DefinitelyTyped/node_modules/dtslint/bin/index.js --onlyTestTsNext
Error: /home/travis/build/DefinitelyTyped/DefinitelyTyped/types/karma-webpack/index.d.ts
ERROR: 29:36  expect  TypeScript@next compile error: 
Namespace 'WebpackDevMiddleware' has no exported member 'Logger'.
ERROR: 30:37  expect  TypeScript@next compile error: 
Namespace 'WebpackDevMiddleware' has no exported member 'Logger'.
ERROR: 31:38  expect  TypeScript@next compile error: 
Namespace 'WebpackDevMiddleware' has no exported member 'Logger'.

I think it's caused by #22267.

karma-webpack is still using 1.12.x of webpack-dev-middleware therefore I added only a local definition of Logger to fix this as there is no v1 typing for webpack-dev-middleware.