The behaviour of the groupBy() function was fixed in 1.1.2 by
3fb91784018de335440b01b3b069fe45dc53e025 to pass only the list of values
to be aggregated to the aggregator function, instead of passing both the
key and the list of values (and expecting both the key and the
aggregated value to be returned). This fix was incompatible with
existing expressions that used the aggregator argument to groupBy().
In the event of an error, fall back trying the previous syntax and see
if something plausible gets returned. If not, re-raise the original error.
This should mean that pre-existing expressions will continue to work,
while most outright bogus expressions should fail in a manner consistent
with the correct definition of the function.
Change-Id: Ic6c54be4ed99003fe56cf1a5329f3f1d84fd43c8
Closes-Bug: #1750032
74cb81b280