Try again

Author: dcherian

xarray/plot/plot.py

@@ -204,12 +204,13 @@ def line(darray, *args, **kwargs):
 
     ax = get_axis(figsize, size, aspect, ax)
 
-    error_msg = 'must be either None or one of %r' % list(darray.dims)
+    error_msg = ('must be either None or one of ({0:s})'
+                 .format(', '.join(['\'' + dd + '\'' for dd in darray.dims])))
 
-    if x not in [None, *darray.dims]:
+    if x is not None and x not in darray.dims:
         raise ValueError('x ' + error_msg)
 
-    if y not in [None, *darray.dims]:
+    if y is not None and y not in darray.dims:
         raise ValueError('y ' + error_msg)
 
     if x is not None and y is not None: