core, plugins: host.getClient now raise an exception instead of returning None when no profile is found, plugins have been adapted consequently and a bit cleaned

src/test/helpers.py

@@ -17,7 +17,6 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-from sat.core.i18n import _
 from sat.core import exceptions
 from constants import Const
 from wokkel.xmppim import RosterItem
@@ -116,7 +115,7 @@ class FakeSAT(object):
         @return: client or None if it doesn't exist"""
         profile = self.memory.getProfileName(profile_key)
         if not profile:
-            return None
+            raise exceptions.ProfileKeyUnknownError
         if profile not in self.profiles:
             self.profiles[profile] = FakeClient(self, profile)
             self.profiles[profile].client_initialized.callback(None)