Critical dependency: the request of a dependency is an expression

[flogy]

Since we have added the fetch polyfill isomorphic-fetch some warning messages occur in the example project log when building the project:

warn gatsby-plugin-mdx
./node_modules/encoding/lib/iconv-loader.js 9:12-34
Critical dependency: the request of a dependency is an expression
    at CommonJsRequireContextDependency.getWarnings
(C:\Users\flogy\Documents\Development\gatsby-mdx-tts-example\node_modules\webpack\lib\dependencies\ContextDependency.js:40:18)
    at Compilation.reportDependencyErrorsAndWarnings
(C:\Users\flogy\Documents\Development\gatsby-mdx-tts-example\node_modules\webpack\lib\Compilation.js:1454:24)
    at hooks.finishModules.callAsync.err (C:\Users\flogy\Documents\Development\gatsby-mdx-tts-example\node_modules\webpack\lib\Compilation.js:1258:10)
    at AsyncSeriesHook.eval [as callAsync] (eval at create
(C:\Users\flogy\Documents\Development\gatsby-mdx-tts-example\node_modules\tapable\lib\HookCodeFactory.js:33:10), <anonymous>:15:1)
    at AsyncSeriesHook.lazyCompileHook (C:\Users\flogy\Documents\Development\gatsby-mdx-tts-example\node_modules\tapable\lib\Hook.js:154:20)
    at Compilation.finish (C:\Users\flogy\Documents\Development\gatsby-mdx-tts-example\node_modules\webpack\lib\Compilation.js:1253:28)
    at hooks.make.callAsync.err (C:\Users\flogy\Documents\Development\gatsby-mdx-tts-example\node_modules\webpack\lib\Compiler.js:672:17)
    at _err0 (eval at create (C:\Users\flogy\Documents\Development\gatsby-mdx-tts-example\node_modules\tapable\lib\HookCodeFactory.js:33:10),
<anonymous>:11:1)
    at _addModuleChain (C:\Users\flogy\Documents\Development\gatsby-mdx-tts-example\node_modules\webpack\lib\Compilation.js:1185:12)
    at processModuleDependencies.err (C:\Users\flogy\Documents\Development\gatsby-mdx-tts-example\node_modules\webpack\lib\Compilation.js:1097:9)
    at process._tickCallback (internal/process/next_tick.js:61:11)
 @ ./node_modules/encoding/lib/encoding.js
 @ ./node_modules/node-fetch/lib/body.js
 @ ./node_modules/node-fetch/index.js
 @ ./node_modules/isomorphic-fetch/fetch-npm-node.js