The use of tasserts in the histogram code causes the log to be flooded with stack traces for the following expected errors:

encountered interval which is unestimatable
direct estimation of $elemMatch is currently only supported for heuristicCE

Those need to be converted to uasserts. Otherwise if any such query is issued during the test, resmoke.py detects assertion-related strings in the mongod log and fails the entire test in a way that can not be worked around.