SharedDict attached as read-only

[mhardcastle]

A new one for me:

• 12:41:53 - AsyncProcessPool [1.3/3.6 7.5/22.6 33.8Gb] process comp28: exception raised processing job FM.Degrid.5.1:F60: Traceback (most recent call last):
  File "/usr/local/src/DDFacet/DDFacet/Other/AsyncProcessPool.py", line 855, in _dispatch_job
  args = [ arg.instantiate() if type(arg) is shared_dict.SharedDictRepresentation else arg for arg in args ]
  File "/usr/local/src/DDFacet/DDFacet/Other/AsyncProcessPool.py", line 855, in
  args = [ arg.instantiate() if type(arg) is shared_dict.SharedDictRepresentation else arg for arg in args ]
  File "/usr/local/src/DDFacet/DDFacet/Array/shared_dict.py", line 49, in instantiate
  return SharedDict(self.path, reset=False, readwrite=self.readwrite, load=self.load)
  File "/usr/local/src/DDFacet/DDFacet/Array/shared_dict.py", line 110, in init
  self.delete()
  File "/usr/local/src/DDFacet/DDFacet/Array/shared_dict.py", line 141, in delete
  raise RuntimeError("SharedDict %s attached as read-only" % self.path)
  RuntimeError: SharedDict /dev/shm/ddf.3442721/DATA:4:0 attached as read-only

Guessing this might be a version of the vm.max_map_count problem? It's 65530 on this machine, which is on a new cluster... If someone can sanity check that guess before I start hassling the sysadmin that would be appreciated.