add error trace in email fetcher

tracim/tracim/lib/base.py

     def debug(self, instance_or_class, message):
         self._logger.debug(Logger.TPL.format(cls=self._txt(instance_or_class), msg=message))
 
-    def error(self, instance_or_class, message):
-        self._logger.error(Logger.TPL.format(cls=self._txt(instance_or_class), msg=message))
+    def error(self, instance_or_class, message, exc_info=0):
+        self._logger.error(Logger.TPL.format(cls=self._txt(instance_or_class), msg=message, exc_info=exc_info))
 
     def info(self, instance_or_class, message):
         self._logger.info(Logger.TPL.format(cls=self._txt(instance_or_class), msg=message))

tracim/tracim/lib/email_fetcher.py

             ))
             self._connection.login(self.user, self.password)
         except Exception as e:
-            log = 'IMAP login error: {}'
-            logger.error(self, log.format(e.__str__()))
+            log = 'Error during execution: {}'
+            logger.error(self, log.format(e.__str__()), exc_info=1)
 
     def _disconnect(self) -> None:
         if self._connection: