SystemError: XML file .. could not be found. is logged to often.

Traceback (most recent call last):
  File "/usr/share/openattic/ceph/models.py", line 213, in set_performance_data_options
    rbds[0].name))
  File "/usr/share/openattic/nagios/graphbuilder.py", line 701, in get_sources_list
    rrd = RRD.get_rrd(host, service)
  File "/usr/share/openattic/nagios/graphbuilder.py", line 696, in get_rrd
    raise SystemError("XML file '{}' could not be found.".format(xmlpath))
SystemError: XML file '/var/lib/pnp4nagios/perfdata/ip-10-0-0-99.ec2.internal/Check_CephRbd_ffc5c3d2-b279-30d0-8e29-9d373d2ff2bc_rbd_aags.xml' could not be found.

grep 'SystemError: XML file ' openattic.log | wc -l
21584