Comment 0 for bug 1537915

Pre-note: due to severe bugs, I had to go down from 3.19.x back to 3.18.6.
I think the following content will speak for itself:

user@mybuntubox:~$ sudo apt-get install --reinstall adwaita-icon-theme
Reading package lists... Done
Building dependency tree
Reading state information... Done
0 to upgrade, 0 to newly install, 1 reinstalled, 0 to remove and 70 not to upgrade.
Need to get 0 B/897 kB of archives.
After this operation, 0 B of additional disk space will be used.
(Reading database ... 307199 files and directories currently installed.)
Preparing to unpack .../adwaita-icon-theme_3.18.0-2ubuntu1_all.deb ...
Unpacking adwaita-icon-theme (3.18.0-2ubuntu1) over (3.18.0-2ubuntu1) ...
Setting up adwaita-icon-theme (3.18.0-2ubuntu1) ...

+++ OKAY. Adwaita Icon Theme is now installed and expected to be working. Version = 3.18.0-2.

user@mybuntubox~$ sudo apt-get install libgtk-3-common=3.18.6-1ubuntu1
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies.
 libgtk-3-common : Depends: adwaita-icon-theme (>= 3.18) but it is not going to be installed
                   Recommends: libgtk-3-0 but it is not going to be installed
E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.

There is clearly something wrong.
Just for "emphasis", I reinstalled Adwaita icon theme 3.18.x again above, to be sure it is really expected to be there.

But it seems to be a bug that libgtk-3-common does not recognize it as there.
Plus, --force-depends appears to be unavailable when using the '=' sign for a version-specific downgrade.