ENH: Add string representation for ImpossibleMergeError

src/caoscrawler/exceptions.py

@@ -20,6 +20,9 @@
 # along with this program. If not, see <https://www.gnu.org/licenses/>.
 #
 
+from typing import Any
+
+
 class ForbiddenTransaction(Exception):
     """Thrown if an transactions is needed that is not allowed.
     For example an update of an entity if the security level is INSERT
@@ -30,12 +33,40 @@ class ForbiddenTransaction(Exception):
 class ImpossibleMergeError(Exception):
     """Thrown if due to identifying information, two SyncNodes  or two Properties of SyncNodes
     should be merged, but there is conflicting information that prevents this.
+
+    Parameters
+    ----------
+    msg : str
+        A case-specific error message describing where the merger error occurred.
+    pname : str
+        The name of the property the values of which caused the merge error.
+    value_a, value_b : Any
+        The two values that couldn't be merged.
+
+    Attributes
+    ----------
+    message : str
+        A case-specific error message describing where the merger error occurred.
+    values : tuple[Any]
+        The two values that couldn't be merged.
+    pname : str
+        The name of the property the values of which caused the merge error.
     """
 
-    def __init__(self, *args, pname, values, **kwargs):
+    def __init__(self, msg: str, pname: str, value_a: Any, value_b: Any):
         self.pname = pname
-        self.values = values
-        super().__init__(self, *args, **kwargs)
+        self.values = (value_a, value_b)
+        self.message = msg
+        super().__init__(self, msg)
+
+    def __str__(self):
+        return (
+            f"{self.message}\n\nThe problematic property is '{self.pname}' with "
+            f"values '{self.values[0]}' and '{self.values[1]}'."
+        )
+
+    def __repr__(self):
+        return self.__str__()
 
 
 class InvalidIdentifiableYAML(Exception):