This happens in 1.8:
[ERROR] console - (node:27731) UnhandledPromiseRejectionWarning: TypeError [ERR_INVALID_CALLBACK]: Callback must be a function
at makeCallback (fs.js:136:11)
at Object.rename (fs.js:578:14)
at doImport (/opt/etherpad-lite/src/node/handler/ImportHandler.js:104:16)
at process._tickCallback (internal/process/next_tick.js:68:7)
This happens when importing a file without known extension in the file name (e.g. no extension at all). As a workaround, you have to set the file name and let it end with an extension, e.g. .txt.
Edit by @muxator: this happens not only when no extension is given, but for every unknown extension (including none) when allowUnknownFileEnds in settings.json is true. Changed the title accordingly.
This happens in 1.8:
This happens when importing a file without known extension in the file name (e.g. no extension at all). As a workaround, you have to set the file name and let it end with an extension, e.g.
.txt.Edit by @muxator: this happens not only when no extension is given, but for every unknown extension (including none) when
allowUnknownFileEndsinsettings.jsonistrue. Changed the title accordingly.