minor changes to _label_1d_plot()

Author: Kevin Donkers

lib/iris/quickplot.py

@@ -141,13 +141,10 @@ def _label_1d_plot(*args, **kwargs):
     else:
         xlabel, ylabel, title = _get_titles(None, args[0])
 
-    if 'axes' in kwargs.keys():
-        axes = kwargs.pop('axes')
-    else:
-        axes = None
+    axes = kwargs.pop('axes', None)
 
     if len(kwargs) != 0:
-        msg = 'Unexpected kwargs {!s} given to _label_1d_plot'.format(
+        msg = 'Unexpected kwargs {} given to _label_1d_plot'.format(
             kwargs.keys())
         raise ValueError(msg)