Bug report

Bug summary

Grid disappear after pcolormesh apply

Code for reproduction

from matplotlib import pyplot as plt
import numpy as np
ax = plt.subplot(111)
ax.grid(True)
ax.pcolormesh(np.arange(7), np.arange(7), np.random.randn(6,6))
ax.set_xlim(-1,7)
plt.show()

Expected outcome

Grid must be visible, but if you apply a pcolormesh after to set grid to True, grid disapear?

Matplotlib version

• Operating system: Ubuntu
• Matplotlib version: 3.1.1
• Matplotlib backend : Qt4Agg
• Python version: 3.7.4

I install library with conda with no options:
conda install matplotlib