Quantities notebook breaks with matplotlib v3.1

[eblur]

CircleCI tests fail on Quantities tutorial now.

plt.figure()
plt.hist(v, bins='auto', histtype="step")
plt.xlabel("Velocity (km/s)")
plt.ylabel("N")
------------------


UnitConversionErrorTraceback (most recent call last)
~/project/venv/lib/python3.6/site-packages/astropy/units/quantity.py in to_value(self, unit, equivalencies)
    708             try:
--> 709                 scale = self.unit._to(unit)
    710             except Exception:

~/project/venv/lib/python3.6/site-packages/astropy/units/core.py in _to(self, other)
    952         raise UnitConversionError(
--> 953             "'{0!r}' is not a scaled version of '{1!r}'".format(self, other))
    954 

UnitConversionError: 'Unit("km / s")' is not a scaled version of 'Unit(dimensionless)'

During handling of the above exception, another exception occurred:

UnitConversionErrorTraceback (most recent call last)
~/project/venv/lib/python3.6/site-packages/astropy/units/quantity.py in __float__(self)
   1079         try:
-> 1080             return float(self.to_value(dimensionless_unscaled))
   1081         except (UnitsError, TypeError):

~/project/venv/lib/python3.6/site-packages/astropy/units/quantity.py in to_value(self, unit, equivalencies)
    711                 # Short-cut failed; try default (maybe equivalencies help).
--> 712                 value = self._to_value(unit, equivalencies)
    713             else:

~/project/venv/lib/python3.6/site-packages/astropy/units/quantity.py in _to_value(self, unit, equivalencies)
    642         return self.unit.to(unit, self.view(np.ndarray),
--> 643                             equivalencies=equivalencies)
    644 

~/project/venv/lib/python3.6/site-packages/astropy/units/core.py in to(self, other, value, equivalencies)
    988         else:
--> 989             return self._get_converter(other, equivalencies=equivalencies)(value)
    990 

~/project/venv/lib/python3.6/site-packages/astropy/units/core.py in _get_converter(self, other, equivalencies)
    919 
--> 920             raise exc
    921 

~/project/venv/lib/python3.6/site-packages/astropy/units/core.py in _get_converter(self, other, equivalencies)
    905             return self._apply_equivalencies(
--> 906                 self, other, self._normalize_equivalencies(equivalencies))
    907         except UnitsError as exc:

~/project/venv/lib/python3.6/site-packages/astropy/units/core.py in _apply_equivalencies(self, unit, other, equivalencies)
    889             "{0} and {1} are not convertible".format(
--> 890                 unit_str, other_str))
    891 

UnitConversionError: 'km / s' (speed) and '' (dimensionless) are not convertible

During handling of the above exception, another exception occurred:

TypeErrorTraceback (most recent call last)
<ipython-input-10-6f08e71ebd86> in <module>
      1 plt.figure()
----> 2 plt.hist(v, bins='auto', histtype="step")
      3 plt.xlabel("Velocity (km/s)")
      4 plt.ylabel("N")

~/project/venv/lib/python3.6/site-packages/matplotlib/pyplot.py in hist(x, bins, range, density, weights, cumulative, bottom, histtype, align, orientation, rwidth, log, color, label, stacked, normed, data, **kwargs)
   2634         align=align, orientation=orientation, rwidth=rwidth, log=log,
   2635         color=color, label=label, stacked=stacked, normed=normed,
-> 2636         **({"data": data} if data is not None else {}), **kwargs)
   2637 
   2638 

~/project/venv/lib/python3.6/site-packages/matplotlib/__init__.py in inner(ax, data, *args, **kwargs)
   1587     def inner(ax, *args, data=None, **kwargs):
   1588         if data is None:
-> 1589             return func(ax, *map(sanitize_sequence, args), **kwargs)
   1590 
   1591         bound = new_sig.bind(ax, *args, **kwargs)

~/project/venv/lib/python3.6/site-packages/matplotlib/axes/_axes.py in hist(self, x, bins, range, density, weights, cumulative, bottom, histtype, align, orientation, rwidth, log, color, label, stacked, normed, **kwargs)
   6723             # make sure we have seen at least one non-nan and finite
   6724             # value before we reset the bin range
-> 6725             if not np.isnan([xmin, xmax]).any() and not (xmin > xmax):
   6726                 bin_range = (xmin, xmax)
   6727 

~/project/venv/lib/python3.6/site-packages/astropy/units/quantity.py in __float__(self)
   1080             return float(self.to_value(dimensionless_unscaled))
   1081         except (UnitsError, TypeError):
-> 1082             raise TypeError('only dimensionless scalar quantities can be '
   1083                             'converted to Python scalars')
   1084 

TypeError: only dimensionless scalar quantities can be converted to Python scalars
TypeError: only dimensionless scalar quantities can be converted to Python scalars

[eblur]

It works in matplotlib version 3.0.2

[eblur]

Opened PR #360

[eblur]

Solved with the above PR.