Add missing ma import

dstansby · dstansby · commit e221ffe9f272 · 2019-06-07T14:01:02.000+01:00
diff --git a/lib/matplotlib/units.py b/lib/matplotlib/units.py
@@ -45,6 +45,7 @@ def default_units(x, axis):
 from numbers import Number
 
 import numpy as np
+from numpy import ma
 
 from matplotlib import cbook
 
