"Unable to open external link" in Evince when google-chrome-unstable is the default browser

TO REPRODUCE:

I attempt to open a URL from a PDF document in Evince.

EXPECTED:

The browser opens the URL.

OBSERVED:

I'm shown an error message:

Unable to open external link
Failed to execute child process “/usr/bin/google-chrome-unstable” (Permission denied)

journalctl shows:

Nov 06 19:19:18 khaeru-laptop audit[22110]: AVC apparmor="DENIED" operation="exec" profile="/usr/bin/evince" name="/opt/google/chrome-unstable/google-chrome-unstable" pid=22110 comm="evince" requested_mask="x" denied_mask="x" fsuid=1000 ouid=0
Nov 06 19:19:18 khaeru-laptop kernel: audit: type=1400 audit(1510013958.773:590): apparmor="DENIED" operation="exec" profile="/usr/bin/evince" name="/opt/google/chrome-unstable/google-chrome-unstable" pid=22110 comm="evince" requested_mask="x" denied_mask="x" fsuid=1000 ouid=0

EXTRA INFORMATION:

- As the messages imply, I'm using Google Chrome "unstable".
- The file
  /usr/bin/google-chrome-unstable
  …is symlinked to:
  /opt/google/chrome-unstable/google-chrome-unstable
- I note that previous bugs, eg. bug #964510, resulted in lines being added to
  /etc/apparmor.d/abstractions/ubuntu-helpers that refer to paths in
  /opt/google/chrome/. This directory does not exist on my system.

$ lsb_release -rd && apt-cache policy apparmor evince google-chrome-unstable
Description: Ubuntu 17.10
Release: 17.10
apparmor:
  Installed: 2.11.0-2ubuntu17
  Candidate: 2.11.0-2ubuntu17
  Version table:
 *** 2.11.0-2ubuntu17 500
        500 http://us.archive.ubuntu.com/ubuntu artful/main amd64 Packages
        100 /var/lib/dpkg/status
evince:
  Installed: 3.26.0-1
  Candidate: 3.26.0-1
  Version table:
 *** 3.26.0-1 500
        500 http://us.archive.ubuntu.com/ubuntu artful/main amd64 Packages
        100 /var/lib/dpkg/status
google-chrome-unstable:
  Installed: 64.0.3251.0-1
  Candidate: 64.0.3253.3-1
  Version table:
     64.0.3253.3-1 500
        500 http://dl.google.com/linux/chrome/deb stable/main amd64 Packages
 *** 64.0.3251.0-1 100
        100 /var/lib/dpkg/status

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: apparmor 2.11.0-2ubuntu17
ProcVersionSignature: Ubuntu 4.13.0-16.19-generic 4.13.4
Uname: Linux 4.13.0-16-generic x86_64
ApportVersion: 2.20.7-0ubuntu3.1
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Mon Nov 6 19:20:34 2017
EcryptfsInUse: Yes
InstallationDate: Installed on 2017-10-11 (26 days ago)
InstallationMedia: Ubuntu 17.04 "Zesty Zapus" - Release amd64 (20170412)
ProcKernelCmdline: BOOT_IMAGE=/boot/vmlinuz-4.13.0-16-generic.efi.signed root=UUID=39ca3c53-0313-4699-a5da-403522e2ff14 ro quiet splash vt.handoff=7
SourcePackage: apparmor
Syslog:

UpgradeStatus: Upgraded to artful on 2017-10-19 (18 days ago)