Improve error messages

Author: ValerianRey

src/torchjd/sparse/_structured_sparse_tensor.py

@@ -59,14 +59,19 @@ def __init__(self, physical: Tensor, strides: Tensor):
             raise ValueError(f"All strides must be non-negative. Found strides={strides}.")
         if strides.shape[1] != physical.ndim:
             raise ValueError(
-                f"strides should have 1 column per physical dimension. Found strides={strides} and physical.shape={physical.shape}."
+                f"strides should have 1 column per physical dimension. Found strides={strides} and "
+                f"physical.shape={physical.shape}."
             )
         if (strides.sum(dim=0) == 0).any():
             raise ValueError(
                 f"strides should not have any column full of zeros. Found strides={strides}."
             )
-        if any(len(group) != 1 for group in get_groupings(list(physical.shape), strides)):
-            raise ValueError(f"Dimensions must be maximally grouped. Found strides={strides}.")
+        groups = get_groupings(list(physical.shape), strides)
+        if any(len(group) != 1 for group in groups):
+            raise ValueError(
+                f"Dimensions must be maximally grouped. Found strides={strides} and "
+                f"groups={groups}"
+            )
 
         self.physical = physical
         self.strides = strides