clearer grammar in error message

TomNicholas · TomNicholas · commit 119864dcb82c · 2021-10-05T14:30:24.000-04:00
diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
@@ -1559,7 +1559,8 @@ def __setitem__(self, key: Union[Hashable, List[Hashable], Mapping], value) -> N
         else:
             if isinstance(value, Dataset):
                 raise TypeError(
-                    "Cannot assign a Dataset to a single key, only a DataArray or Variable object"
+                    "Cannot assign a Dataset to a single key - only a DataArray or Variable object can be stored under"
+                    "a single key."
                 )
             self.update({key: value})
 

Original file line number	Diff line number	Diff line change
`@@ -1559,7 +1559,8 @@ def __setitem__(self, key: Union[Hashable, List[Hashable], Mapping], value) -> N`
`1559`	`1559`	`else:`
`1560`	`1560`	`if isinstance(value, Dataset):`
`1561`	`1561`	`raise TypeError(`
`1562`		`- "Cannot assign a Dataset to a single key, only a DataArray or Variable object"`
	`1562`	`+ "Cannot assign a Dataset to a single key - only a DataArray or Variable object can be stored under"`
	`1563`	`+ "a single key."`
`1563`	`1564`	`)`
`1564`	`1565`	`self.update({key: value})`
`1565`	`1566`