Rally requires a team repo even if used as a load generator

[danielmitterdorfer]

When the team repository is not present and Rally is not able to clone it, benchmarks with the pipeline benchmark-only will fail with:

[ERROR] Cannot race. ("Error on host [{'host': '127.0.0.1', 'port': 9200}]", [~/.rally/benchmarks/teams/default] must be a git repository.

However, there is no point in requiring this git repo because Rally would not use it anyway when used as a load generator (i.e. --pipeline=benchmark-only)

relevant logs:

2018-01-16 13:45:23,167 PID:14958 rally.racecontrol INFO Asking mechanic to start the engine.
2018-01-16 13:45:23,171 PID:14959 rally.mechanic INFO MechanicActor#receiveMessage(msg = [<class 'esrally.mechanic.mechanic.StartEngine'>] sender = [ActorAddr-(T|:60526)])
2018-01-16 13:45:23,171 PID:14959 rally.mechanic INFO Received signal from race control to start engine.
2018-01-16 13:45:23,172 PID:14959 rally.metrics INFO Opening metrics store for invocation=[20180116T134520Z], track=[geonames], challenge=[append-no-conflicts], car=[['external']]
2018-01-16 13:45:23,172 PID:14959 rally.mechanic INFO Cluster will not be provisioned by Rally.
2018-01-16 13:45:23,172 PID:14959 rally.actor INFO Capabilities [{'coordinator': True, 'ip': '127.0.0.1', 'Convention Address.IPv4': '127.0.0.1:1900', 'Thespian ActorSystem Name': 'multiprocTCPBase', 'Thespian ActorSystem Version': 2, 'Thespian Watch Supported': True, 'Python Version': (3, 6, 4, 'final', 0), 'Thespian Generation': (3, 8), 'Thespian Version': '1516110321131'}] match requirements [{'coordinator': True}].
2018-01-16 13:45:23,184 PID:15024 rally.mechanic INFO Connecting to externally provisioned nodes on [[{'host': '127.0.0.1', 'port': 9200}]].
2018-01-16 13:45:23,189 PID:15024 rally.metrics INFO Opening metrics store for invocation=[20180116T134520Z], track=[geonames], challenge=[append-no-conflicts], car=[['external']]
2018-01-16 13:45:23,190 PID:15024 rally.mechanic ERROR Cannot process message [<esrally.mechanic.mechanic.StartNodes object at 0x10aadc6d8>]
Traceback (most recent call last):
  File "~/Projects/rally/esrally/mechanic/mechanic.py", line 446, in receiveMessage
    msg.distribution, msg.external, msg.docker)
  File "~/Projects/rally/esrally/mechanic/mechanic.py", line 501, in create
    repo = team.team_repo(cfg)
  File "~/Projects/rally/esrally/mechanic/team.py", line 95, in team_repo
    current_team_repo = repo.RallyRepository(remote_url, teams_dir, repo_name, "teams", offline)
  File "~/Projects/rally/esrally/utils/repo.py", line 35, in __init__
    .format(src=self.repo_dir))
esrally.exceptions.SystemSetupError: ('[~/.rally/benchmarks/teams/default] must be a git repository.\n\nPlease run:\ngit -C ~/.rally/benchmarks/teams/default init', None)
2018-01-16 13:45:23,193 PID:14959 rally.mechanic INFO MechanicActor#receiveMessage(msg = [<class 'esrally.actor.BenchmarkFailure'>] sender = [ActorAddr-(T|:60545)])
2018-01-16 13:45:23,194 PID:14958 rally.racecontrol INFO BenchmarkActor#receiveMessage(msg = [<class 'esrally.actor.BenchmarkFailure'>] sender = [ActorAddr-(T|:60529)])
2018-01-16 13:45:23,194 PID:14958 rally.racecontrol INFO Received a benchmark failure from [ActorAddr-(T|:60529)] and will forward it now.
2018-01-16 13:45:23,195 PID:14947 rally.racecontrol ERROR A benchmark failure has occurred

As long as git is available on the machine, the current workaround is:

mkdir -p ~/.rally/benchmarks/teams/default
cd ~/.rally/benchmarks/teams/default
git init
touch .gitignore
git add .
git commit -m "Initial commit"