flask.ext has been deprecated for years now and should actually have been logging a warning to console ever since too. OctoPrint 1.4.1 had to update the flask dependencies due to security considerations and in the new flask version the old compatibility layer still allowing flask.ext to work got removed.
Which means this plugin no longer will load on OctoPrint 1.4.1+ unless this PR gets merged and a new release (1.5.1?) pushed out.
See also the discussion in OctoPrint/OctoPrint#3643
flask.ext has been deprecated for years now and should actually have been logging a warning to console ever since too. OctoPrint 1.4.1 had to update the flask dependencies due to security considerations and in the new flask version the old compatibility layer still allowing flask.ext to work got removed.
Which means this plugin no longer will load on OctoPrint 1.4.1+ unless this PR gets merged and a new release (1.5.1?) pushed out.
See also the discussion in OctoPrint/OctoPrint#3643