crash when a file disappears...

@petersilva is already working on this.

Since Nov 8, 2022.

```
2022-11-05 23:56:23,627 [INFO] 2 files will be ingested
2022-11-05 23:56:23,631 [INFO] (944 Bytes) Ingested in DB as /var/spool/px/db/20221105/WXAPP-HOURLY_OBS/DMS/CMC_dms-op1-host05/2400633.yte.hourly_obs.en.json:DMS:CMC_dms-op1-host05:WXAPP-HOURLY_OBS:JSON::20221105235623
2022-11-05 23:56:23,631 [INFO] Queued for: wxo-ops-be02-wxapp wxo-ops-be01-wxapp ddsr-MSC-DMS-OP-PDS wxo-op-be06-wxapp wxo-op-be07-wxapp pxi-dms wxo-op-be05-wxapp
2022-11-05 23:56:23,635 [INFO] (947 Bytes) Ingested in DB as /var/spool/px/db/20221105/WXAPP-HOURLY_OBS/DMS/CMC_dms-op1-host05/2400633.yte.hourly_obs.fr.json:DMS:CMC_dms-op1-host05:WXAPP-HOURLY_OBS:JSON::20221105235623
2022-11-05 23:56:23,635 [INFO] Queued for: wxo-ops-be02-wxapp wxo-ops-be01-wxapp ddsr-MSC-DMS-OP-PDS wxo-op-be06-wxapp wxo-op-be07-wxapp pxi-dms wxo-op-be05-wxapp
Traceback (most recent call last):
File "/usr/bin/pxReceiver", line 150, in
source.ingestor.ingestSingleFile(igniter)
File "/usr/lib/px/Ingestor.py", line 376, in ingestSingleFile
reader.read()
File "/usr/lib/px/DiskReader.py", line 101, in read
self.sort()
File "/usr/lib/px/DiskReader.py", line 303, in sort
templist = [ (os.stat(file)[ST_MTIME],file) for file in self.files]
OSError: [Errno 2] No such file or directory: '/var/spool/px/rxq/dms-v2-products/kjfk.202211052351.hourly_avipads.xml:DMS:CMC_dms-op1-host02:AVIPADS-HOURLYOBS:XML'
Traceback (most recent call last):
File "/usr/bin/pxReceiver", line 130, in
igniter = PXIgniter('receiver', sourceName, command, lockPath, logger)
File "/usr/lib/px/PXIgniter.py", line 37, in __init__
eval("self." + cmd)() # Execute the command directly
File "/usr/lib/px/Igniter.py", line 136, in restart
self.stop()
File "/usr/lib/px/PXIgniter.py", line 80, in stop
os.kill(self.lockpid, signal.SIGTERM)
OSError: [Errno 1] Operation not permitted
Traceback (most recent call last):
File "/usr/bin/pxReceiver", line 150, in
source.ingestor.ingestSingleFile(igniter)
File "/usr/lib/px/Ingestor.py", line 376, in ingestSingleFile
reader.read()
File "/usr/lib/px/DiskReader.py", line 101, in read
self.sort()
File "/usr/lib/px/DiskReader.py", line 303, in sort
templist = [ (os.stat(file)[ST_MTIME],file) for file in self.files]
OSError: [Errno 2] No such file or directory: '/var/spool/px/rxq/dms-v2-products/1060r0k.wwl.hourly_obs.en.json:DMS:CMC_dms-op1-host05:WXAPP-HOURLY_OBS:JSON'
```