os.makedirs race condition

[turmon]

Describe the bug
A race condition when creating a cache directory causes an Exception

To Reproduce

Traceback (most recent call last):
  File "/gpfs/scratch/exo-yield/Sandbox/hwo/Local/sandbox_driver.py", line 380, in <module>
    message = main(args, xspecs)
              ^^^^^^^^^^^^^^^^^^
  File "/gpfs/scratch/exo-yield/Sandbox/hwo/Local/sandbox_driver.py", line 269, in main
    sim = EXOSIMS.MissionSim.MissionSim(args.scriptfile, **xspecs)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/gpfs/scratch/exo-yield/Sandbox/Python-venvs/exosims-202509-YUrun-mjt/EXOSIMS/EXOSIMS/MissionSim.py", line 167, in __init__
    self.SurveySimulation = get_module(
                            ^^^^^^^^^^^
  File "/gpfs/scratch/exo-yield/Sandbox/Python-venvs/exosims-202509-YUrun-mjt/EXOSIMS/EXOSIMS/SurveySimulation/coroOnlyScheduler.py", line 64, in __init__
    SurveySimulation.__init__(self, **specs)
  File "/gpfs/scratch/exo-yield/Sandbox/Python-venvs/exosims-202509-YUrun-mjt/EXOSIMS/EXOSIMS/Prototypes/SurveySimulation.py", line 262, in __init__
    self.cachedir = get_cache_dir(cachedir)
                    ^^^^^^^^^^^^^^^^^^^^^^^
  File "/gpfs/scratch/exo-yield/Sandbox/Python-venvs/exosims-202509-YUrun-mjt/EXOSIMS/EXOSIMS/util/get_dirs.py", line 203, in get_cache_dir
    cache_dir = get_exosims_dir("cache", cachedir)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/gpfs/scratch/exo-yield/Sandbox/Python-venvs/exosims-202509-YUrun-mjt/EXOSIMS/EXOSIMS/util/get_dirs.py", line 127, in get_exosims_dir
    os.makedirs(indir)
  File "<frozen os>", line 225, in makedirs
FileExistsError: [Errno 17] File exists: 'sims/Yokohama_Ultimate.fam/Trials.fam/TimeMultiplyAdd-v4.exp/Caches/s_YU_VIS_D7.42_iwa029_C2.30e-10_nf1.01e-12_att0.216_sn0.440'

==== The relevant lines from get_exosims_dir are:

   124          # if it doesn't exist, try creating it
   125          if not (os.path.isdir(indir)):
   126              try:
   127                  os.makedirs(indir)
   128              except PermissionError:
   129                  print("Cannot create directory: {indir}.")
   130  

This happens because the directory was created between the time os.path.isdir() is run, and os.makedirs() is run
(TOCTOU)

I'd suggest either:

• Also catching "FileExistsError" in addition to PermissionError.
• Using the exist_ok=True optional argument to os.makedirs()

Expected behavior
No exception.

JSON script:

EXOSIMS version:

• v3.6.5

Additional context
On the JPL supercomputer, writing to a device using a GPFS storage system. There is only one process writing to or creating this directory (because the exception happens while a canary process is generating cache files). Nevertheless, it does happen (exceptions on 3 runs out of 768).