Compilation error on Ubuntu 14.04

[JanosSarkoezi]

Hi Corwind,

very nice script, but on

LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 14.04.5 LTS
Release:    14.04
Codename:   trusty

got this error on compiling vte

## -------------- ##
## Configuration. ##
## -------------- ##

Configuration for libvte 0.44.1 for gtk+-3.0
    GNUTLS: yes
    PCRE2: no
    Installing Glade catalogue: no
    Debugging: no
    Introspection: yes
    Vala bindings: yes
    Test application: yes

... some warnings ...

  CXX      libvte_2_91_la-vteaccess.lo
  CXX      libvte_2_91_la-vtegtk.lo
  CXX      libvte_2_91_la-vteseq.lo
  CXX      libvte_2_91_la-vteresources.lo
  CXX      libvte_2_91_la-vtetypebuiltins.lo
  CXXLD    libvte-2.91.la
  GISCAN   Vte-2.91.gir
 VAPIGEN vte-2.91.vapi
  VALAC    vte_2_91_vala.stamp
app.vala:23.23-23.33: error: The type name `Gtk.Popover' could not be found
class SearchPopover : Gtk.Popover
                      ^^^^^^^^^^^
Compilation failed: 1 error(s), 0 warning(s)

Please help to solve this problem.