`hwlatdetect`: Permission denied: '/proc/mounts'

AppArmor log:

= AppArmor =
Time: Jun 13 19:58:11
Log: apparmor="DENIED" operation="open" class="file" profile="snap.rt-tests.hwlatdetect" name="/proc/1593027/mounts" pid=1593027 comm="python3" requested_mask="r" denied_mask="r" fsuid=0 ouid=0
File: /proc/1593027/mounts (read)
Suggestions:
* adjust program to not access '@{PROC}/@{pid}/mounts'
* add one of 'mount-control, mount-observe, network-control, steam-support' to 'plugs'

Runtime error:

Traceback (most recent call last):
  File "/snap/rt-tests/6/usr/sbin/hwlatdetect", line 442, in <module>
    detect = Tracer()
             ^^^^^^^^
  File "/snap/rt-tests/6/usr/sbin/hwlatdetect", line 268, in __init__
    super().__init__()
  File "/snap/rt-tests/6/usr/sbin/hwlatdetect", line 129, in __init__
    self.debugfs = DebugFS()
                   ^^^^^^^^^
  File "/snap/rt-tests/6/usr/sbin/hwlatdetect", line 49, in __init__
    with open('/proc/mounts') as f:
         ^^^^^^^^^^^^^^^^^^^^
PermissionError: [Errno 13] Permission denied: '/proc/mounts'

canonical / rt-tests-snap

`hwlatdetect`: Permission denied: '/proc/mounts' #11