And, for anyone interested, here is the output of aptitude after the
backports repository has been disabled:

$ sudo aptitude install libgtkhtml-4.0-0:i386
The following NEW packages will be installed:
at-spi2-core{a} glib-networking:i386{a} libaspell15:i386{ab} libatk-bridge2.0-0:i386{a} libatspi2.0-0:i386{a}
libcairo-gobject2:i386{a} libcolord2:i386{a} libenchant1c2a:i386{a} libgail-3-0:i386{a} libgtk-3-0:i386{a}
libgtkhtml-4.0-0:i386{b} libhunspell-1.3-0:i386{a} libjson-glib-1.0-0:i386{a} liblcms2-2:i386{a} libproxy1:i386{a}
librest-0.7-0:i386{a} libsoup-gnome2.4-1:i386{a} libsoup2.4-1:i386{a} libsqlite3-0:i386{ab} libudev1:i386{a}
libwayland-client0:i386{a} libwayland-cursor0:i386{a} libxkbcommon0:i386{a} libxml2:i386{ab}
The following packages are RECOMMENDED but will NOT be installed:
colord colord:i386 enchant:i386
0 packages upgraded, 24 newly installed, 0 to remove and 4 not upgraded.
Need to get 6,456 kB of archives. After unpacking 20.6 MB will be used.
The following packages have unmet dependencies:
libaspell15 : Breaks: libaspell15:i386 (!= 0.60.7~20110707-3) but 0.60.7~20110707-1.3 is to be installed.
libaspell15:i386 : Breaks: libaspell15 (!= 0.60.7~20110707-1.3) but 0.60.7~20110707-3 is installed.
libsqlite3-0 : Breaks: libsqlite3-0:i386 (!= 3.8.7.4-1) but 3.8.7.1-1+deb8u1 is to be installed.
libsqlite3-0:i386 : Breaks: libsqlite3-0 (!= 3.8.7.1-1+deb8u1) but 3.8.7.4-1 is installed.
libxml2 : Breaks: libxml2:i386 (!= 2.9.2+dfsg1-3) but 2.9.1+dfsg1-5+deb8u2 is to be installed.
libxml2:i386 : Breaks: libxml2 (!= 2.9.1+dfsg1-5+deb8u2) but 2.9.2+dfsg1-3 is installed.
libgtkhtml-4.0-0:i386 : Depends: libgtkhtml-4.0-common:i386 (= 4.8.5-1) which is a virtual package.
The following actions will resolve these dependencies:

      Keep the following packages at their current version:
1)      libaspell15:i386 [Not Installed]                   
2)      libenchant1c2a:i386 [Not Installed]                
3)      libgail-3-0:i386 [Not Installed]                   
4)      libgtk-3-0:i386 [Not Installed]                    
5)      libgtkhtml-4.0-0:i386 [Not Installed]              
6)      librest-0.7-0:i386 [Not Installed]                 
7)      libsoup-gnome2.4-1:i386 [Not Installed]            
8)      libsoup2.4-1:i386 [Not Installed]                  
9)      libsqlite3-0:i386 [Not Installed]                  
10)     libxml2:i386 [Not Installed]                       

Accept this solution? [Y/n/q/?] q
Abandoning all efforts to resolve these dependencies.
Abort.

--

"The optimist proclaims that we live in the best of all
possible worlds. The pessimist fears this is true."

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