[pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Author: pre-commit-ci[bot]

lib/iris/cube.py

@@ -174,12 +174,12 @@ def __str__(self):
 
     def __repr__(self):
         """Runs repr on every cube."""
-        return '[%s]' % ',\n'.join([repr(cube) for cube in self])
+        return "[%s]" % ",\n".join([repr(cube) for cube in self])
 
     @staticmethod
     def _assert_is_cube(obj):
         if not isinstance(obj, Cube):
-            msg = ("Object of type '{}' does not belong in a cubelist.")
+            msg = "Object of type '{}' does not belong in a cubelist."
             raise ValueError(msg.format(type(obj).__name__))
 
     @staticmethod