The below bugs appers when running esrally

Hi @danielmitterdorfer

Now I running as user not root, running as another user named "elasticsearch".
When I running, I occur the same problem as Esrally - Couldn't find a tar.gz distribution when building from sources.

Your know, My gradle is 2.13 and my java is 1.8, just like:
[root@laoyang config]# echo $JAVA_HOME
/opt/jdk1.8.0_91
[root@laoyang config]# gradle
:help

Welcome to Gradle 2.13.

But I still have errors as follow:
2016-08-08-05-31-29/local/logs/rally_out.log).
[elasticsearch@laoyang bin]$ esrally

____        ____

/ __ ____ / / / __
/ // / __ `/ / / / / /
/ , / // / / / // /
/
/ ||_,///_, /
/____/

Writing additional logs to /home/elasticsearch/.rally/benchmarks/races/2016-08-08-05-36-47/local/logs/rally_out.log

Preparing for race (might take a few moments) ...
Downloading sources from https://github.com/elastic/elasticsearch.git to /home/elasticsearch/.rally/benchmarks/src.
Cloning into '/home/elasticsearch/.rally/benchmarks/src'...
remote: Counting objects: 648049, done.
remote: Compressing objects: 100% (31/31), done.
remote: Total 648049 (delta 3), reused 0 (delta 0), pack-reused 648012
Receiving objects: 100% (648049/648049), 233.02 MiB | 145.00 KiB/s, done.
Resolving deltas: 100% (364756/364756), done.
Checking connectivity... done.
Building from sources ...

ERROR: Cannot race

Reason: Couldn't find a tar.gz distribution.

Please check the log file [/home/elasticsearch/.rally/benchmarks/races/2016-08-08-05-36-47/local/logs/rally_out.log] for further details first.

If you need further help, please check Rally's docs at https://esrally.readthedocs.io or ask a question in the forum at https://discuss.elastic.co/c/elasticsearch.

If you think this is a bug, please file a report at https://github.com/elastic/rally/issues and include the log file for this race (/home/elasticsearch/.rally/benchmarks/races/2016-08-08-05-36-47/local/logs/rally_out.log).

2016-08-08 06:20:19,438 rally.builder INFO Executing /usr/bin/gradle clean...
273 2016-08-08 06:30:03,814 rally.builder WARNING Executing '/usr/bin/gradle clean' failed
274 2016-08-08 06:30:03,816 rally.builder INFO Executing /usr/bin/gradle :distribution:tar:assemble...
275 2016-08-08 06:35:50,65 rally.builder WARNING Executing '/usr/bin/gradle :distribution:tar:assemble' failed
276 2016-08-08 06:35:50,67 root ERROR Cannot run subcommand [race].
277 Traceback (most recent call last):
278 File "/usr/local/python3/lib/python3.5/site-packages/esrally/mechanic/builder.py", line 31, in add_binary_to_config
279 binary = glob.glob("%s/distribution/tar/build/distributions/*.tar.gz" % src_dir)[0]
280 IndexError: list index out of range
281
282 During handling of the above exception, another exception occurred:
283
284 Traceback (most recent call last):
285 File "/usr/local/python3/lib/python3.5/site-packages/esrally/rally.py", line 302, in dispatch_sub_command
286 racecontrol.run(cfg)
287 File "/usr/local/python3/lib/python3.5/site-packages/esrally/racecontrol.py", line 336, in run
288 pipeline()
289 File "/usr/local/python3/lib/python3.5/site-packages/esrally/racecontrol.py", line 58, in call
290 step()
291 File "/usr/local/python3/lib/python3.5/site-packages/esrally/racecontrol.py", line 27, in call
292 self.command(self.ctx)
293 File "/usr/local/python3/lib/python3.5/site-packages/esrally/racecontrol.py", line 274, in
294 PipelineStep("find-candidate", ctx, lambda ctx: ctx.mechanic.find_candidate()),
295 File "/usr/local/python3/lib/python3.5/site-packages/esrally/mechanic/mechanic.py", line 31, in find_candidate
296 self._builder.add_binary_to_config()
297 File "/usr/local/python3/lib/python3.5/site-packages/esrally/mechanic/builder.py", line 33, in add_binary_to_config
298 raise ImproperlyConfigured("Couldn't find a tar.gz distribution.")
299 esrally.exceptions.ImproperlyConfigured: Couldn't find a tar.gz distribution

For summary: The above error is
ERROR: Cannot race
Reason: Couldn't find a tar.gz distribution.
esrally.exceptions.ImproperlyConfigured: Couldn't find a tar.gz distribution

I think the tips should tell me which .tar.gz is needed?

If your know the detail, please told me. Thanks very much.