saveAsTextFile() + -getmerge returning empty file

[rafrombrc]

From https://bugzilla.mozilla.org/show_bug.cgi?id=1373633

Sequence of events:
In Spark:
serialized_beta_full[1].saveAsTextFile("s3://net-mozaws-prod-us-west-2-pipeline-analysis/ekr/serialized-beta-full.out")

In hadoop:
hadoop fs -getmerge s3://net-mozaws-prod-us-west-2-pipeline-analysis/ekr/serialized-beta-full.out serialized-beta-full.out

This claims to copy a lot of files, but the result is 0-length.