[Ubuntu 20.04 LTS] -Error: ENOSPC: System limit for number of file watchers reached

Listen uses inotify by default on Linux to monitor directories for changes.

You can get your current inotify file watch limit by executing:

$ cat /proc/sys/fs/inotify/max_user_watches

You can set a new limit temporary with:

$ sudo sysctl fs.inotify.max_user_watches=524288
$ sudo sysctl -p

If you like to make your limit permanent, use:

$ echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf
$ sudo sysctl -p