Breaks gatsby develop whenever I yarn add a package

[asktree]

Whenever I yarn add a package, gatsby develop starts returning this error

It doesn't go away until I restart gatsby develop. Eats a lot of my time.

[oliviertassinari]

We are following the same approach to implement the plugin as https://github.com/gatsbyjs/gatsby/tree/master/packages/gatsby-plugin-typography. They also likely have this issue.