log error message instead of traceback

ceod/model/Group.py

@@ -1,5 +1,4 @@
 import json
-import traceback
 from typing import List, Union
 
 import ldap3
@@ -92,8 +91,8 @@ class Group:
         try:
             with self.ldap_srv.entry_ctx_for_group(self) as entry:
                 entry.uniqueMember.add(dn)
-        except ldap3.core.exceptions.LDAPAttributeOrValueExistsResult:
-            logger.error(traceback.format_exc())
+        except ldap3.core.exceptions.LDAPAttributeOrValueExistsResult as err:
+            logger.warning(err)
             raise UserAlreadyInGroupError()
         self.members.append(username)
 
@@ -102,7 +101,7 @@ class Group:
         try:
             with self.ldap_srv.entry_ctx_for_group(self) as entry:
                 entry.uniqueMember.delete(dn)
-        except ldap3.core.exceptions.LDAPCursorError:
-            logger.error(traceback.format_exc())
+        except ldap3.core.exceptions.LDAPCursorError as err:
+            logger.warning(err)
             raise UserNotInGroupError()
         self.members.remove(username)