make qtsass watchdog dependence optional

[ewerybody]

Heya! Just for clearing up all the things discussed:

Agreed, we can make it optional then, make sure to update the setup.py

What needs to happen there? You mean just like

• removing line 75? 'watchdog'
• also in requirements.txt line 2?

That aint all right?

[danbradham]

After thinking about this a little bit I think I'd like to do the following:

1. Create a watchers subpackage containing a Watcher baseclass.
2. Create a watchdog implementation of the Watcher API.
3. Import a Watcher implementation in the api.watch function just prior to use.

This would concentrate the point of failure in a single location making it easier to manage. It would also allow us to create fallback implementations.

A QT Watcher would probably make more sense than watchdog as we can be somewhat sure that QT would be available in a project using qtsass. There's one issue here in that the QFileSystemWatcher is actually pretty incomplete. It doesn't handle recursive directory watching and requires a QApplication event loop to work at all if I remember correctly.

We could also write a simple polling Watcher that polls the filesystem in a thread checking modified times of files and folders. This is roughly equivalent to watchdogs fallback Observer. If we went this route we could eliminate watchdog as a dependency entirely.

I think I have some bandwidth to put together a wip PR for this tomorrow. At the bare minimum tackling the first 3 steps I listed above.

[ccordoba12]

If watchdog is used for development only, why not adding it to extras_require instead of reinventing the wheel?

[goanpeca]

Agreed with @ccordoba12 here @danbradham

Th fix for this was to add an extras_require on setup.py. Or add the try except on imports since this is not really a crucial functionality