Hi,

cairomm-1.14 is defined as:

(define-public cairomm-1.14
  (package
    (inherit cairomm)
    [...]
    (propagated-inputs
     (modify-inputs (package-propagated-inputs cairomm)
       (prepend libsigc++-2)))))

Because cairomm already has a libsigc++ (@3), and 'prepend' is used
instead of 'replace', this causes cairomm@1.14 to have both versions
of libsigc++ as inputs.  It appears to be introduced with commit
736c5df29ac380413ec45b496c63dcf80672712d.

Unfortunately, according to "guix refresh -l", fixing this will cause
1980 rebuilds (staging branch?).

The attached patch (currently targetting master) fixes it (cairomm 
builds).  I'll try to compile an application with the new cairomm
and report if it works.

Greetings,
Maxime.