flake8 fix.

Author: dcherian

xarray/tests/test_plot.py

@@ -107,7 +107,7 @@ def test_1d_x_y_kw(self):
 
         for aa, (x, y) in enumerate(xy):
             da.plot(x=x, y=y, ax=ax.flat[aa])
-            ax.flat[aa].set_title('x=' + str(x) + ' | '+'y='+str(y))
+            ax.flat[aa].set_title('x=' + str(x) + ' | ' + 'y=' + str(y))
 
         with raises_regex(ValueError, 'cannot'):
             da.plot(x='z', y='z')