Failure to process a repo that was previously being processed correctly

[fatfreddie]

(on behalf of another person)
I'm importing some depots, and it is not working the way it was early this year.
I was able to import depots at the beginning of this year, and I re-run the importation of already imported depots and I the process is halted due to an error, apparently it doesn't find any transactions on a stream or something like that. What it comes to my attention is that it shows the same error if I run another importation of a depot that was successfully imported back early this year.
I un-defined importation of empty streams (without any promote), as the first error messages sort of pointed that out, but then it failed on streams that do have promoted code, so I'm not sure what else to try.
(I have been quietly investigating and have some changes to push, for testing)

[fatfreddie]

The output from running python3 ac2git.py --verbose was

Running time was  0:01:25.25
The script has encountered an exception, aborting!
Traceback (most recent call last):
  File "ac2git.py", line 4080, in AccuRev2GitMain
    rv = state.Start(isRestart=args.restart, isSoftRestart=args.softRestart)
  File "ac2git.py", line 3304, in Start
    self.RetrieveStreams()
  File "ac2git.py", line 1631, in RetrieveStreams
    tr, commitHash = self.RetrieveStream(depot=depot, stream=streamInfo, dataRef=dataRef, stateRef=stateRef, hwmRef=hwmRef, startTransaction=self.config.accurev.startTransaction, endTransaction=endTr.id)
  File "ac2git.py", line 1576, in RetrieveStream
    stateTr, stateHash = self.RetrieveStreamInfo(depot=depot, stream=stream, stateRef=stateRef, startTransaction=startTransaction, endTransaction=endTransaction)
  File "ac2git.py", line 1286, in RetrieveStreamInfo
    deepHist = accurev.ext.deep_hist(depot=depot, stream=stream.name, timeSpec="{0}-{1}".format(tr.id, endTr.id), ignoreTimelocks=ignoreTimelocks, useCache=self.config.accurev.UseCommandCache())
  File "/home/robertsmithson/ac2git/accurev.py", line 2676, in deep_hist
    timelockTs = ext.restrict_timespec_to_timelock(depot=streamInfo.depotName, timeSpec=parentTs, timelock=streamInfo.time)
  File "/home/robertsmithson/ac2git/accurev.py", line 2551, in restrict_timespec_to_timelock
    preLockTr = hist(depot=depot, timeSpec=UTCDateTimeOrNone(timelock)).transactions[0]
AttributeError: 'NoneType' object has no attribute 'transactions'
Traceback (most recent call last):
  File "ac2git.py", line 4100, in <module>
    AccuRev2GitMain(sys.argv)
  File "ac2git.py", line 4080, in AccuRev2GitMain
    rv = state.Start(isRestart=args.restart, isSoftRestart=args.softRestart)
  File "ac2git.py", line 3304, in Start
    self.RetrieveStreams()
  File "ac2git.py", line 1631, in RetrieveStreams
    tr, commitHash = self.RetrieveStream(depot=depot, stream=streamInfo, dataRef=dataRef, stateRef=stateRef, hwmRef=hwmRef, startTransaction=self.config.accurev.startTransaction, endTransaction=endTr.id)
  File "ac2git.py", line 1576, in RetrieveStream
    stateTr, stateHash = self.RetrieveStreamInfo(depot=depot, stream=stream, stateRef=stateRef, startTransaction=startTransaction, endTransaction=endTransaction)
  File "ac2git.py", line 1286, in RetrieveStreamInfo
    deepHist = accurev.ext.deep_hist(depot=depot, stream=stream.name, timeSpec="{0}-{1}".format(tr.id, endTr.id), ignoreTimelocks=ignoreTimelocks, useCache=self.config.accurev.UseCommandCache())
  File "/home/robertsmithson/ac2git/accurev.py", line 2676, in deep_hist
    timelockTs = ext.restrict_timespec_to_timelock(depot=streamInfo.depotName, timeSpec=parentTs, timelock=streamInfo.time)
  File "/home/robertsmithson/ac2git/accurev.py", line 2551, in restrict_timespec_to_timelock
    preLockTr = hist(depot=depot, timeSpec=UTCDateTimeOrNone(timelock)).transactions[0]
AttributeError: 'NoneType' object has no attribute 'transactions'