3D quiver plot fails when pivot = "middle"

[andrej5elin]

Bug report

Bug summary

In matplotlib 3.1.1. ax.quiver(*data, pivot = "middle") in 3d projection wont work when 'length' parameter is integer.

Code for reproduction

import matplotlib.pyplot as plt
import numpy as np

fig = plt.figure()
ax = fig.gca(projection='3d')

# Make the grid
x, y, z = np.meshgrid(np.arange(-0.8, 1, 0.2),
                      np.arange(-0.8, 1, 0.2),
                      np.arange(-0.8, 1, 0.8))

# Make the direction data for the arrows
u = np.sin(np.pi * x) * np.cos(np.pi * y) * np.cos(np.pi * z)
v = -np.cos(np.pi * x) * np.sin(np.pi * y) * np.cos(np.pi * z)
w = (np.sqrt(2.0 / 3.0) * np.cos(np.pi * x) * np.cos(np.pi * y) *
     np.sin(np.pi * z))

#ok
ax.quiver(x, y, z, u, v, w, length = 1., pivot = "middle")

#this fails
ax.quiver(x, y, z, u, v, w, length = 1, pivot = "middle")

plt.show()

Actual outcome

UFuncTypeError: Cannot cast ufunc 'subtract' output from dtype('float64') to dtype('int64') with casting rule 'same_kind'

Expected outcome

This used to work in previous versions... (can't remember which).

Matplotlib version

• Operating system: OSX
• Matplotlib version: 3.1.1
• Matplotlib backend (print(matplotlib.get_backend())): Qt5Agg
• Python version: 3.7.
• Jupyter version (if applicable):
• Other libraries:

installed from conda-forge

[ImportanceOfBeingErnest]

#12796