App should raise an Exception on misconfigured view_decorator

[spiqueras]

If the user has provided a view_decorator, and this decorator fails to be imported, django-plotly-dash will default to no decoration as it swallows all exceptions.

django-plotly-dash/django_plotly_dash/access.py

Lines 36 to 48 in 4edb730

	try:
	dash_view_decorator_name = settings.PLOTLY_DASH['view_decorator']
	try:
	dash_view_decorator = locals()[dash_view_decorator_name]
	except:
	mod_name, func_name = dash_view_decorator_name.rsplit('.', 1)
	if mod_name:
	mod = importlib.import_module(mod_name)
	dash_view_decorator = getattr(mod, func_name)
	else:
	dash_view_decorator = locals()[func_name]
	except:
	dash_view_decorator = None

It'd be more sensible to raise an exception in such cases (maybe ImproperlyConfigured?), so the user is immediately notified of their error and can fix it. Technically a breaking change but hopefully one for the better.