Fix typo

Author: edouardberthe

lib/matplotlib/units.py

@@ -29,7 +29,7 @@ def axisinfo(unit, axis):
                 return None
             majloc = dates.AutoDateLocator()
             majfmt = dates.AutoDateFormatter(majloc)
-            return AxisInfo(majloc=majloc, majfmt=majfmt, label='date')
+            return units.AxisInfo(majloc=majloc, majfmt=majfmt, label='date')
 
         @staticmethod
         def default_units(x, axis):