And the apparmor denials:

Sep 28 14:08:52 ubuntu kernel: [   68.309885] audit: type=1400 audit(1538143732.840:232): apparmor="DENIED" operation="open" profile="snap-update-ns.gnome-calculator" name="/upper/snap/" pid=6535 comm="3" requested_mask="r" denied_mask="r" fsuid=0 ouid=0
Sep 28 14:08:52 ubuntu kernel: [   68.309908] audit: type=1400 audit(1538143732.840:233): apparmor="DENIED" operation="open" profile="snap-update-ns.gnome-calculator" name="/upper/snap/" pid=6535 comm="3" requested_mask="r" denied_mask="r" fsuid=0 ouid=0
Sep 28 14:08:52 ubuntu kernel: [   68.310069] audit: type=1400 audit(1538143732.840:234): apparmor="DENIED" operation="open" profile="snap-update-ns.gnome-calculator" name="/upper/snap/" pid=6535 comm="3" requested_mask="r" denied_mask="r" fsuid=0 ouid=0
Sep 28 14:08:52 ubuntu kernel: [   68.310240] audit: type=1400 audit(1538143732.840:235): apparmor="DENIED" operation="open" profile="snap-update-ns.gnome-calculator" name="/upper/snap/" pid=6535 comm="3" requested_mask="r" denied_mask="r" fsuid=0 ouid=0
Sep 28 14:08:52 ubuntu kernel: [   68.310345] audit: type=1400 audit(1538143732.840:236): apparmor="DENIED" operation="open" profile="snap-update-ns.gnome-calculator" name="/upper/snap/" pid=6535 comm="3" requested_mask="r" denied_mask="r" fsuid=0 ouid=0
Sep 28 14:08:52 ubuntu kernel: [   68.310448] audit: type=1400 audit(1538143732.840:237): apparmor="DENIED" operation="open" profile="snap-update-ns.gnome-calculator" name="/upper/snap/" pid=6535 comm="3" requested_mask="r" denied_mask="r" fsuid=0 ouid=0
Sep 28 14:08:52 ubuntu kernel: [   68.310508] audit: type=1400 audit(1538143732.840:238): apparmor="DENIED" operation="open" profile="snap-update-ns.gnome-calculator" name="/upper/snap/" pid=6535 comm="3" requested_mask="r" denied_mask="r" fsuid=0 ouid=0
Sep 28 14:08:52 ubuntu kernel: [   68.310580] audit: type=1400 audit(1538143732.840:239): apparmor="DENIED" operation="open" profile="snap-update-ns.gnome-calculator" name="/upper/snap/" pid=6535 comm="3" requested_mask="r" denied_mask="r" fsuid=0 ouid=0
Sep 28 14:08:52 ubuntu kernel: [   68.310647] audit: type=1400 audit(1538143732.840:240): apparmor="DENIED" operation="open" profile="snap-update-ns.gnome-calculator" name="/upper/snap/" pid=6535 comm="3" requested_mask="r" denied_mask="r" fsuid=0 ouid=0
Sep 28 14:08:52 ubuntu kernel: [   68.310709] audit: type=1400 audit(1538143732.840:241): apparmor="DENIED" operation="open" profile="snap-update-ns.gnome-calculator" name="/upper/snap/" pid=6535 comm="3" requested_mask="r" denied_mask="r" fsuid=0 ouid=0
Sep 28 14:09:12 ubuntu kernel: [   87.483763] audit: type=1400 audit(1538143752.012:268): apparmor="DENIED" operation="open" profile="snap.gnome-calculator.gnome-calculator" name="/etc/pulse/client.conf" pid=6528 comm="gnome-calculato" requested_mask="r" denied_mask="r" fsuid=999 ouid=0
Sep 28 14:09:12 ubuntu kernel: [   87.485499] audit: type=1400 audit(1538143752.016:269): apparmor="DENIED" operation="mknod" profile="snap.gnome-calculator.gnome-calculator" name="/dev/shm/pulse-shm-3251133329" pid=6528 comm="gnome-calculato" requested_mask="c" denied_mask="c" fsuid=999 ouid=999
Sep 28 14:09:12 ubuntu kernel: [   87.486695] audit: type=1400 audit(1538143752.016:270): apparmor="DENIED" operation="connect" profile="snap.gnome-calculator.gnome-calculator" name="/run/user/999/pulse/native" pid=6528 comm="gnome-calculato" requested_mask="wr" denied_mask="wr" fsuid=999 ouid=999