Adjust ufunc error message

Based on the correct observation in pydata#8179 (comment) (slightly adjusted message)

Author: max-sixty

xarray/core/computation.py

@@ -17,6 +17,7 @@
 from xarray.core.alignment import align, deep_align
 from xarray.core.common import zeros_like
 from xarray.core.duck_array_ops import datetime_to_numeric
+from xarray.core.formatting import limit_lines
 from xarray.core.indexes import Index, filter_indexes_from_coords
 from xarray.core.merge import merge_attrs, merge_coordinates_without_align
 from xarray.core.options import OPTIONS, _get_keep_attrs
@@ -769,8 +770,8 @@ def func(*arrays):
         raise ValueError(
             f"applied function does not have the number of "
             f"outputs specified in the ufunc signature. "
-            f"Result is not a tuple of {signature.num_outputs} elements:\n\n"
-            f"{short_array_repr(result_data)}"
+            f"Received a {type(result_data)} with {len(result_data)} elements instead:\n\n"
+            f"{limit_lines(result_data, limit=10)}"
         )
 
     objs = _all_of_type(args, Variable)