import matplotlib.pyplot as plt
import matplotlib.colors as mcolor
import matplotlib.cm as cm

norm = mcolor.SymLogNorm(5)

fig, ax = plt.subplots()
fig.colorbar(cm.ScalarMappable(norm=norm, cmap='viridis'), cax=ax)

Traceback (most recent call last):
  File "test.py", line 8, in <module>
    fig.colorbar(cm.ScalarMappable(norm=norm, cmap='viridis'), cax=ax)
  File "/Users/dstansby/github/matplotlib/lib/matplotlib/figure.py", line 2201, in colorbar
    cb = cbar.colorbar_factory(cax, mappable, **cb_kw)
  File "/Users/dstansby/github/matplotlib/lib/matplotlib/colorbar.py", line 1686, in colorbar_factory
    cb = Colorbar(cax, mappable, **kwargs)
  File "/Users/dstansby/github/matplotlib/lib/matplotlib/colorbar.py", line 1210, in __init__
    ColorbarBase.__init__(self, ax, **kwargs)
  File "/Users/dstansby/github/matplotlib/lib/matplotlib/colorbar.py", line 472, in __init__
    self.draw_all()
  File "/Users/dstansby/github/matplotlib/lib/matplotlib/colorbar.py", line 495, in draw_all
    self._process_values()
  File "/Users/dstansby/github/matplotlib/lib/matplotlib/colorbar.py", line 945, in _process_values
    b = self.norm.inverse(self._uniform_y(self.cmap.N + 1))
  File "/Users/dstansby/github/matplotlib/lib/matplotlib/colors.py", line 1276, in inverse
    val = val * (self._upper - self._lower) + self._lower
AttributeError: 'SymLogNorm' object has no attribute '_upper'