Syntax Error: Error: PostCSS received undefined instead of CSS string

报错：Syntax Error: Error: PostCSS received undefined instead of CSS string

npm rebuild node-sass

报错：npm i canvas 报错 canvas@2.11.2 run install node-pre-gyp install --fallback-to-build --update-binary

npm install canvas --canvas_binary_host_mirror=https://registry.npmmirror.com/-/binary/canvas

node版本报错

npm install node-sass@6.0.1