LALInference: Matplotlib key error

The LALInference test suite is failing with the following error:

 Traceback (most recent call last):
  File "/builds/duncanmmacleod/lalsuite/conda/bld/lalinference_1595343513543/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_plac/lib/python3.8/site-packages/matplotlib/__init__.py", line 677, in __setitem__
    cval = self.validate[key](val)
KeyError: 'text.latex.unicode'
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
  File "/builds/duncanmmacleod/lalsuite/conda/bld/lalinference_1595343513543/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_plac/lib/python3.8/site-packages/matplotlib/__init__.py", line 990, in rc
    rcParams[key] = v
  File "/builds/duncanmmacleod/lalsuite/conda/bld/lalinference_1595343513543/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_plac/lib/python3.8/site-packages/matplotlib/__init__.py", line 682, in __setitem__
    raise KeyError(
KeyError: 'text.latex.unicode is not a valid rc parameter (see rcParams.keys() for a list of valid parameters)'
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
  File "/builds/duncanmmacleod/lalsuite/conda/bld/lalinference_1595343513543/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_plac/bin/cbcBayesPlotSpinDisk", line 17, in <module>
    rc('text.latex', unicode=True)
  File "/builds/duncanmmacleod/lalsuite/conda/bld/lalinference_1595343513543/_test_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_plac/lib/python3.8/site-packages/matplotlib/__init__.py", line 992, in rc
    raise KeyError(('Unrecognized key "%s" for group "%s" and '
KeyError: 'Unrecognized key "text.latex.unicode" for group "text.latex" and name "unicode"'

Full build log is here. Can you please take a look at this ASAP?