ENH: A bit more informative error message.

src/caosdb/apiutils.py

@@ -46,8 +46,7 @@ from caosdb.exceptions import CaosDBException
 
 class EntityMergeConflictError(CaosDBException):
     """An error that is raised in case of an unresolvable conflict when merging
-    to entities.
-
+    two entities.
     """
 
 
@@ -372,13 +371,14 @@ def empty_diff(old_entity: Entity, new_entity: Entity, compare_referenced_record
     return True
 
 
-def merge_entities(entity_a: Entity, entity_b: Entity, merge_references_with_empty_diffs=True, force=False):
+def merge_entities(entity_a: Entity, entity_b: Entity, merge_references_with_empty_diffs=True,
+                   force=False):
     """Merge entity_b into entity_a such that they have the same parents and properties.
 
     datatype, unit, value, name and description will only be changed in entity_a
     if they are None for entity_a and set for entity_b. If there is a
-    corresponding value for entity_a different from None an
-    EntityMergeConflictError will be raised informing of an unresolvable merge
+    corresponding value for entity_a different from None, an
+    EntityMergeConflictError will be raised to inform about an unresolvable merge
     conflict.
 
     The merge operation is done in place.
@@ -476,7 +476,8 @@ def merge_entities(entity_a: Entity, entity_b: Entity, merge_references_with_emp
                 setattr(entity_a, special_attribute, sa_b)
             else:
                 raise EntityMergeConflictError(
-                    f"Conflict in special attribute {special_attribute}.")
+                    f"Conflict in special attribute {special_attribute}:\n"
+                    f"A: {sa_a}\nB: {sa_b}")
     return entity_a