improve error messaging in to_edge_transform_and_lower (pytorch#7184)

Summary:

when sanity checks fail, the error message isn't super useful because we don't know what node or what op target is the violating one. We improve the error message here so that we can see what it is.

Reviewed By: tarun292

Differential Revision: D66787170

Author: mcr229

exir/program/_program.py

@@ -880,9 +880,10 @@ def _sanity_check_graph_for_non_decomp_ops(
     generate_error=False,
     partitioner_name=None,
 ):
-    warning_str = f"Found {ops_set_to_not_decompose} in edge dialect program {name}."
+    warning_str_end = ""
     if partitioner_name is not None:
-        warning_str += f" This op was registered by the partitioner {partitioner_name} to not be decomposed."
+        warning_str_end += f"This op was registered by the partitioner {partitioner_name} to not be decomposed.\n"
+    warning_str_end += f"The following ops: {ops_set_to_not_decompose} were specified to not be decomposed in {name}."
 
     # Check that the ops that were registered to not be decomposed are not present in the
     # graph anymore as the transform passes and backends should have consumed them by now.
@@ -894,6 +895,10 @@ def _sanity_check_graph_for_non_decomp_ops(
         if (
             node.op == "call_function" and node.target in ops_set_to_not_decompose
         ) and is_op_supported:
+            warning_str = (
+                f"Node {node} with op {node.target} was not decomposed or delegated.\n" 
+                + warning_str_end
+            )
             if generate_error:
                 raise RuntimeError(warning_str)
             else:
@@ -904,6 +909,10 @@ def _sanity_check_graph_for_non_decomp_ops(
             if (
                 node.op == "call_function" and node.target in ops_set_to_not_decompose
             ) and is_op_supported:
+                warning_str = (
+                    f"Node {node} with op {node.target} was not decomposed or delegated.\n" 
+                    + warning_str_end
+                )
                 if generate_error:
                     raise RuntimeError(warning_str)
                 else: