capturing recon error

src/databricks/labs/ucx/queries/migration/main/03_1_data_reconciliation_status.sql

@@ -1,4 +1,4 @@
--- viz type=table, name=Migration status, search_by=table_name,upgraded_status, columns=table_name,object_type,table_format,location,upgraded_status,upgraded_to_table_name,schema_matches,column_comparison,data_matches,source_row_count,target_row_count,source_missing_count,target_missing_count,view_text,storage_properties,is_partitioned
+-- viz type=table, name=Migration status, search_by=table_name,upgraded_status, columns=table_name,object_type,table_format,location,upgraded_status,upgraded_to_table_name,schema_matches,column_comparison,data_matches,source_row_count,target_row_count,source_missing_count,target_missing_count,reconciliation_error,view_text,storage_properties,is_partitioned
 -- widget title=Migration status, row=3, col=0, size_x=8, size_y=16
 SELECT
   concat_ws('.', tables.`catalog`, tables.`database`, tables.name) AS table_name,
@@ -17,6 +17,7 @@ SELECT
   reconciliation_results.target_row_count,
   reconciliation_results.source_missing_count,
   reconciliation_results.target_missing_count,
+  reconciliation_results.error_message as reconciliation_error,
   tables.view_text,
   tables.storage_properties,
   tables.is_partitioned

src/databricks/labs/ucx/queries/views/reconciliation_results.sql

@@ -24,6 +24,7 @@ SELECT
   data_comparison_result.target_row_count,
   data_comparison_result.source_missing_count,
   data_comparison_result.target_missing_count,
-  schema_comparison_result.data AS column_comparison
+  schema_comparison_result.data AS column_comparison,
+  error_message
 FROM
   flattened

src/databricks/labs/ucx/recon/migration_recon.py

@@ -27,10 +27,11 @@ class ReconResult:
     dst_catalog: str
     dst_schema: str
     dst_table: str
-    schema_matches: bool
-    data_matches: bool
-    schema_comparison: str
-    data_comparison: str
+    schema_matches: bool = False
+    data_matches: bool = False
+    schema_comparison: str | None = None
+    data_comparison: str | None = None
+    error_message: str | None = None
 
 
 class MigrationRecon(CrawlerBase[ReconResult]):
@@ -108,7 +109,14 @@ def _recon(
             data_comparison = self._data_comparator.compare_data(source, target, compare_rows)
         except DatabricksError as e:
             logger.warning(f"Error while comparing {source.fqn_escaped} and {target.fqn_escaped}: {e}")
-            return None
+            return ReconResult(
+                source.schema,
+                source.table,
+                target.catalog,
+                target.schema,
+                target.table,
+                error_message=str(e),
+            )
         recon_results = ReconResult(
             source.schema,
             source.table,