gtk-update-icon-cache: The generated cache was invalid

[ghost]

Reporter info

• Distribution - (run lsb_release -a)

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 18.10
Release:    18.10
Codename:   cosmic

• Gtk+ 3.0 version - (run apt policy libgtk-3-0)

  $ apt policy libgtk-3-0
  libgtk-3-0:
  Installed: 3.24.1-1ubuntu2
  Candidate: 3.24.1-1ubuntu2
  Version table:
  *** 3.24.1-1ubuntu2 500
      500 http://archive.ubuntu.com/ubuntu cosmic/main amd64 Packages
      100 /var/lib/dpkg/status

• Desktop environment - XFCE 4.12

Is this issue an Icon Request? NO

Please note that Icon Requests are considered low-priority. We recommend submitting Icon Requests directly to upstream Papirus

Pop version (if you knew)

1.3.0~1546553893~18.10~e586523

Related Application and/or Shell theming (or name of widget)

What is this?

Actual issue

The installation from the PPA repository gives a warning: "gtk-update-icon-cache: The generated cache was invalid."

Steps to reproduce (if you knew)

$ sudo apt-get install --reinstall pop-icon-theme
Reading package lists... Done
Building dependency tree       
Reading state information... Done
0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 60 not upgraded.
Need to get 7.495 kB of archives.
After this operation, 0 B of additional disk space will be used.
Get:1 http://ppa.launchpad.net/system76/pop/ubuntu cosmic/main amd64 pop-icon-theme all 1.3.0~1546553893~18.10~e586523 [7.495 kB]
Fetched 7.495 kB in 8s (937 kB/s)                                                                                                             
(Reading database ... 465145 files and directories currently installed.)
Preparing to unpack .../pop-icon-theme_1.3.0~1546553893~18.10~e586523_all.deb ...
Unpacking pop-icon-theme (1.3.0~1546553893~18.10~e586523) over (1.3.0~1546553893~18.10~e586523) ...
gtk-update-icon-cache: The generated cache was invalid.
WARNING: icon cache generation failed for /usr/share/icons/Pop
Setting up pop-icon-theme (1.3.0~1546553893~18.10~e586523) ...
gtk-update-icon-cache: The generated cache was invalid.
WARNING: icon cache generation failed for /usr/share/icons/Pop

Expected behaviour

Installation without warnings

Behaviour in Adwaita

?

Other Note (feature-request, question, etc...)