Bug report

Bug summary

When I try to save an animation using imagemagick to write to a gif, the saving works perfectly, but the message MovieWriter imagemagick unavailable. is printed to the console.

Code for reproduction

from matplotlib.animation import FuncAnimation
import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(0, 1, 20)

def f(x, i):
    return x*np.sin(i/10)

line, = plt.plot(x, f(x, 0))
plt.xlim([0,1])
plt.ylim([-1,1])
fig = plt.gcf()
def animate(i):
    line.set_data(x, f(x,i))

anim = FuncAnimation(fig, animate, frames=60, interval=50)
anim.save('fig.gif', writer='imagemagick')
plt.show()

Actual outcome

MovieWriter imagemagick unavailable.

Yet, the gif is still produced.

Expected outcome

The gif is produced without lying to me about the unavailability of imagemagick.

Matplotlib version

• Operating system: Windows 10 Version 1803
• Matplotlib version: 2.2.2
• Matplotlib backend (print(matplotlib.get_backend())): Qt5Agg
• Python version: 3.6.5 (installed with conda)
• Other libraries: imagemagick 7.0.8.7 (installed with chocolatey)

I suspect this has to do with that way that I've installed imagemagick, since chocolatey shims "magick" into the PATH, and matplotlib looks through the registry.