When using a container of type singularity, error occuring when testing a wrapper

Did someone tried to set test inside a wrapper using singularity?

I always get this? even if everything look fine.

```
Traceback (most recent call last):
File "/usr/lib/python2.7/unittest/case.py", line 329, in run
testMethod()
File "/tmp/tmpIm1X92/galaxy-dev/test/functional/test_toolbox.py", line 99, in test_tool
self.do_it(tool_version=tool_version, test_index=test_index)
File "/tmp/tmpIm1X92/galaxy-dev/test/functional/test_toolbox.py", line 36, in do_it
verify_tool(tool_id, self.galaxy_interactor, resource_parameters=resource_parameters, test_index=test_index, tool_version=tool_version, register_job_data=register_job_data)
File "/tmp/tmpIm1X92/galaxy-dev/lib/galaxy/tools/verify/interactor.py", line 753, in verify_tool
raise e
JobOutputsError: need more than 1 value to unpack
```

Start by reproducing the Singularity wrapper test described in test/functional/test_toolbox.py and follow the failure into lib/galaxy/tools/verify/interactor.py at verify_tool. Inspect the JobOutputsError traceback and determine why the test output handling fails; done means the wrapper test completes successfully without the unpacking error.

Written by the indexing model from the issue text.