Locking issue while sync is paused

When UI tries to update database while sync is on pause, a lock can occurs as the exception used to pause the thread dont close the session : no commit, no rollback

The locking issue is also visible in AutoUpdate :
Traceback (most recent call last):
File "C:\Users\LZ\Documents\GitHub\nuxeo-drive\nuxeo-drive-client\nxdrive\gui\
application.py", line 341, in action_update
self.update_version, self.updater)
File "C:\Users\LZ\Documents\GitHub\nuxeo-drive\nuxeo-drive-client\nxdrive\gui\
update_prompt.py", line 130, in prompt_update
controller.is_auto_update(), callback=update)
File "C:\Users\LZ\Documents\GitHub\nuxeo-drive\nuxeo-drive-client\nxdrive\cont
roller.py", line 375, in is_auto_update
device_config=device_config).auto_update
File "C:\Users\LZ\Documents\GitHub\nuxeo-drive\nuxeo-drive-client\nxdrive\cont
roller.py", line 362, in get_general_settings
dc = (self.get_device_config() if device_config is None
File "C:\Users\LZ\Documents\GitHub\sharp-cpo-clients\clouddesktop-drive\cloudd
esktop\controller\controller.py", line 65, in get_device_config
return session.query(CPODeviceConfig).one()
File "C:\Python27\Lib\site-packages\sqlalchemy\orm\query.py", line 2361, in on
e
ret = list(self)
File "C:\Python27\Lib\site-packages\sqlalchemy\orm\query.py", line 2404, in __
iter__
return self._execute_and_instances(context)
File "C:\Python27\Lib\site-packages\sqlalchemy\orm\query.py", line 2419, in _e
xecute_and_instances
result = conn.execute(querycontext.statement, self._params)
File "C:\Python27\Lib\site-packages\sqlalchemy\engine\base.py", line 720, in e
xecute
return meth(self, multiparams, params)
File "C:\Python27\Lib\site-packages\sqlalchemy\sql\elements.py", line 317, in
_execute_on_connection
return connection._execute_clauseelement(self, multiparams, params)
File "C:\Python27\Lib\site-packages\sqlalchemy\engine\base.py", line 817, in _
execute_clauseelement
compiled_sql, distilled_params
File "C:\Python27\Lib\site-packages\sqlalchemy\engine\base.py", line 947, in _
execute_context
context)
File "C:\Python27\Lib\site-packages\sqlalchemy\engine\base.py", line 1108, in
_handle_dbapi_exception
exc_info
File "C:\Python27\Lib\site-packages\sqlalchemy\util\compat.py", line 185, in r
aise_from_cause
reraise(type(exception), exception, tb=exc_tb)
File "C:\Python27\Lib\site-packages\sqlalchemy\engine\base.py", line 940, in _
execute_context
context)
File "C:\Python27\Lib\site-packages\sqlalchemy\engine\default.py", line 435, i
n do_execute
cursor.execute(statement, parameters)
sqlalchemy.exc.OperationalError: (OperationalError) database is locked u'SELECT
device_config.device_id AS device_config_device_id, device_config.client_version
AS device_config_client_version, device_config.proxy_config AS device_config_pr
oxy_config, device_config.proxy_type AS device_config_proxy_type, device_config.
proxy_server AS device_config_proxy_server, device_config.proxy_port AS device_c
onfig_proxy_port, device_config.proxy_authenticated AS device_config_proxy_authe
nticated, device_config.proxy_username AS device_config_proxy_username, device_c
onfig.proxy_password AS device_config_proxy_password, device_config.proxy_except
ions AS device_config_proxy_exceptions, device_config.auto_update AS device_conf
ig_auto_update, device_config.autostart AS device_config_autostart, device_confi
g.icon_overlays AS device_config_icon_overlays, device_config.notifications AS d
evice_config_notifications, device_config.log AS device_config_log \nFROM device
_config' ()