PID not found after OOM

[pbordron]

When minimap2 (or mashmap) is killed because of an OOM, dgenies-scheduler fails this way:

Traceback (most recent call last):
  File "/.../venv/dgenies/lib/python3.x/site-packages/dgenies/bin/local_scheduler.py", line 429, in <module>
     scheduler.start()
  File "/.../venv/dgenies/lib/python3.x/site-packages/dgenies/bin/local_scheduler.py", line 55, in start
     started_jobs, cluster_started_jobs = self.parse_started_jobs()
                                          ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/.../venv/dgenies/lib/python3.x/site-packages/dgenies/bin/local_scheduler.py", line 238, in parse_started_jobs
     if job.status != "started" or psutil.pid_exists(pid):
                                   ^^^^^^^^^^^^^^^^^^^^^^
   File "/.../venv/dgenies/lib64/python3.x/site-packages/psutil/__init__.py", line 1408, in pid_exists
      if pid < 0:
       ^^^^^^^
 TypeError: '<' not supported between instances of 'NoneType' and 'int'