def _find_impl(cls, role, interface):
"""
Find relation implementation based on its role and interface.
"""
# The module has already been discovered and imported.
module = 'relations.{}.{}'.format(interface, role)
if module not in sys.modules:
try:
_append_path(hookenv.charm_dir())
_append_path(os.path.join(hookenv.charm_dir(), 'hooks'))
importlib.import_module(module)
except ImportError:
return None
return cls._find_subclass(sys.modules[module])
def _relation_module(role, interface):
"""
Return module for relation based on its role and interface, or None.
Prefers new location (reactive/relations) over old (hooks/relations).
"""
_append_path(hookenv.charm_dir())
_append_path(os.path.join(hookenv.charm_dir(), 'hooks'))
base_module = 'relations.{}.{}'.format(interface, role)
for module in ('reactive.{}'.format(base_module), base_module):
if module in sys.modules:
break
try:
importlib.import_module(module)
break
except ImportError:
continue
else:
hookenv.log('Unable to find implementation for relation: '
'{} of {}'.format(role, interface), hookenv.ERROR)
return None
return sys.modules[module]