---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-3-b77d6298b805> in <module>()
      6 units = pint.UnitRegistry()
      7 fig, axes = plt.subplots(1, 1)
----> 8 axes.axhline(0 * units.meter)

~/miniconda3/envs/py36/lib/python3.6/site-packages/matplotlib/axes/_axes.py in axhline(self, y, xmin, xmax, **kwargs)
    720         self._process_unit_info(ydata=y, kwargs=kwargs)
    721         yy = self.convert_yunits(y)
--> 722         scaley = (yy < ymin) or (yy > ymax)
    723 
    724         trans = self.get_yaxis_transform(which='grid')

~/miniconda3/envs/py36/lib/python3.6/site-packages/pint/quantity.py in <lambda>(self, other)
   1075                   other.to_root_units().magnitude)
   1076 
-> 1077     __lt__ = lambda self, other: self.compare(other, op=operator.lt)
   1078     __le__ = lambda self, other: self.compare(other, op=operator.le)
   1079     __ge__ = lambda self, other: self.compare(other, op=operator.ge)

~/miniconda3/envs/py36/lib/python3.6/site-packages/pint/quantity.py in compare(self, other, op)
   1065                 return op(self._convert_magnitude_not_inplace(UnitsContainer()), other)
   1066             else:
-> 1067                 raise ValueError('Cannot compare Quantity and {0}'.format(type(other)))
   1068 
   1069         if self._units == other._units:

ValueError: Cannot compare Quantity and <class 'numpy.float64'>