Bug report

Bug summary
Logarithmic scaling seems to break the label formatting.

Code for reproduction

import matplotlib.pyplot as plt
from matplotlib import ticker
import numpy as np


p = np.linspace(1000, 500, 100)
T = np.linspace(300, 200, p.size)


fig, ax = plt.subplots()
ax.plot(T, p)
ax.set_yscale('log')
ax.yaxis.set_major_formatter(ticker.StrMethodFormatter('{x:.3f}'))

plt.show()

The issue is reproducible using different Formatters (e.g. FuncFormatter, ...).

Actual outcome

Expected outcome
I would expect the axis to use the passed Formatter like the linear scaled axis does:

Matplotlib version

• Operating System: macOS Sierra (10.12.4) | Debian GNU/Linux 8.6
• Matplotlib Version: 2.0.0
• Python Version: 3.6.1

Matplotlib was installed from the conda-forge channel.

Thanks for your great work!

/Lukas