import and export fail to give a green 'Done' line after extension update

[caver456]

When the extension gets updated, the background scripts from the previous version of the extension are still alive in each tab. When the new content script tries to talk to the old background scripts, everything fails, with the noted error in the content script.

https://github.com/sourcegraph/sourcegraph/issues/4413
https://stackoverflow.com/questions/53939205

[caver456]

Former title of this issue: 'extension context invalidated' error in background.js after extension update

Changing the title to indicate the symptom that the user would see, and reopening since the symptom remains.

The easy solution is to reload the page.