Error with lb-run when using python3

Using python3 in conda, I install the LBCORE-1654.support-container-in-lb-run branch of LbEnv, and try:

lb-run --debug  --container singularity --platform x86_64-centos7-gcc7-opt LHCb/v50r1 gaudirun.py --option "from DetDescChecks.Options import LoadDDDBTest; LoadDDDBTest('2018')"

I get:

DEBUG:Environment:loading /cvmfs/lhcb.cern.ch/lib/lhcb/DBASE/TCK/L0TCK/v5r32/TCK_L0TCK.xenv
Traceback (most recent call last):
  File "/data/ramp/conda3/envs/lbenv/lib/python3.7/site-packages/LbEnv/ProjectEnv/script.py", line 939, in main
    super(LbRun, self).main()
  File "/data/ramp/conda3/envs/lbenv/lib/python3.7/site-packages/xenv/__init__.py", line 289, in main
    self._makeEnv()
  File "/data/ramp/conda3/envs/lbenv/lib/python3.7/site-packages/LbEnv/ProjectEnv/script.py", line 860, in _makeEnv
    self.overrideGridMiddleware()
  File "/data/ramp/conda3/envs/lbenv/lib/python3.7/site-packages/LbEnv/ProjectEnv/script.py", line 618, in overrideGridMiddleware
    checksum.update(x)
TypeError: Unicode-objects must be encoded before hashing