ReFrame cannot resolve the stage dir if the default value is used

[teojgo]

The default value of stagedir is ./stage/ and ReFrame cannot resolve the path:

./bin/reframe -C config/cscs.py -n GREASYCheck_serial_gpu_24_12_1_1 -r -R -c cscs-checks/
[ReFrame Setup]
  version:           3.0-dev6 (rev: dfe9a400)
  command:           './bin/reframe -C config/cscs.py -nGREASYCheck_serial_gpu_24_12_1_1 -r -R -c cscs-checks/'
  launched by:       manitart@dom101
  working directory: '/users/manitart/reframe_dev_public'
  check search path: (R) '/users/manitart/reframe_dev_public/cscs-checks'
  stage directory:   './stage/'
  output directory:  './output/'
  performance logs:  './perflogs'

[==========] Running 1 check(s)
[==========] Started on Thu May  7 11:48:46 2020 

[----------] started processing GREASYCheck_serial_gpu_24_12_1_1 (GREASYCheck_serial_gpu_24_12_1_1)
[ RUN      ] GREASYCheck_serial_gpu_24_12_1_1 on dom:gpu using PrgEnv-gnu
[----------] finished processing GREASYCheck_serial_gpu_24_12_1_1 (GREASYCheck_serial_gpu_24_12_1_1)

[----------] waiting for spawned checks to finish
[     FAIL ] (1/1) GREASYCheck_serial_gpu_24_12_1_1 on dom:gpu using PrgEnv-gnu
[----------] all spawned checks have finished

[  FAILED  ] Ran 1 test case(s) from 1 check(s) (1 failure(s))
[==========] Finished on Thu May  7 11:50:02 2020 

==============================================================================
SUMMARY OF FAILURES
------------------------------------------------------------------------------
FAILURE INFO for GREASYCheck_serial_gpu_24_12_1_1 
  * System partition: dom:gpu
  * Environment: PrgEnv-gnu
  * Stage directory: ./stage/dom/gpu/PrgEnv-gnu/GREASYCheck_serial_gpu_24_12_1_1
  * Node list: nid00042,nid00041
  * Job type: batch job (id=1013554)
  * Maintainers: ['VH', 'SK']
  * Failing phase: sanity
  * Rerun with '-n GREASYCheck_serial_gpu_24_12_1_1 -p PrgEnv-gnu --system dom:gpu'
  * Reason: OS error: [Errno 2] No such file or directory: './stage/dom/gpu/PrgEnv-gnu/GREASYCheck_serial_gpu_24_12_1_1'
------------------------------------------------------------------------------

[vkarak]

The problem is that stagedir et al. are not stored as absolute paths anymore and this test relies on that.

[teojgo]

Indeed, the stage dir should not be passed in os.listdir in https://github.com/eth-cscs/reframe/blob/625ce43d724c13343c6c693066a0db3ee4fb3c5e/cscs-checks/apps/greasy/greasy_check.py#L142
The default value that uses the current dir fixes the problem

[vkarak]

Perhaps we should fix that in the framework nonetheless.