Bare Exceptions

[T4rk1n]

Currently, there is a couple bare Exception that are raised by dash, they should be refactored into appropriate DashException.

Should be a TypeError or NoLayoutException:

dash/dash/dash.py

Lines 197 to 203 in 54ca4a3

	if (not isinstance(value, Component) and
	not isinstance(value, collections.Callable)):
	raise Exception(
	''
	'Layout must be a dash component '
	'or a function that returns '
	'a dash component.')

A new exception type InvalidIndexException:

dash/dash/dash.py

Lines 224 to 229 in 54ca4a3

	if missing:
	raise Exception(
	'Did you forget to include {} in your index string ?'.format(
	', '.join('{%' + x + '%}' for x in missing)
	)
	)

dash/dash/dash.py

Lines 409 to 415 in 54ca4a3

	plural = 's' if len(missing) > 1 else ''
	raise Exception(
	'Missing element{pl} {ids} in index.'.format(
	ids=', '.join(missing),
	pl=plural
	)
	)

A new exception type DependencyException:

dash/dash/dash.py

Lines 357 to 374 in 54ca4a3

	if package_name not in self.registered_paths:
	raise Exception(
	'Error loading dependency.\n'
	'"{}" is not a registered library.\n'
	'Registered libraries are: {}'
	.format(package_name, list(self.registered_paths.keys())))
	elif path_in_package_dist not in self.registered_paths[package_name]:
	raise Exception(
	'"{}" is registered but the path requested is not valid.\n'
	'The path requested: "{}"\n'
	'List of registered paths: {}'
	.format(
	package_name,
	path_in_package_dist,
	self.registered_paths
	)
	)

ResourceException ?:

dash/dash/resources.py

Lines 42 to 48 in 54ca4a3

	raise Exception(
	'{} does not have a '
	'relative_package_path, absolute_path, or an '
	'external_url.'.format(
	json.dumps(filtered_resource)
	)
	)

[ned2]

@shammamah, just spotted one that slipped through. Sorry to be a bit late before you merged the PR. On line 400:

raise Exception(
    'Serving files from absolute_path isn\'t supported yet'
)

Perhaps NotImplementedException or NotSupportedYetExcpetion