Black could make single-line strings over multiple lines (i.e. a number of single quotes strings on multiple lines surrounded by parentheses) more efficient, by resizing them to the full length of the line.

Even if that was overreach, there's a peculiar situation where you end up with multiple strings on the same line, like below:

-        warnings.warn('Dataset.sel_points is deprecated: use Dataset.sel()'
-                      'instead.', DeprecationWarning, stacklevel=2)
-
+        warnings.warn(
+            'Dataset.sel_points is deprecated: use Dataset.sel()' 'instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )