ROS Melodic binary error "Qt not found"

[matlabbe]

http://build.ros.org/job/Mbin_uB64__find_object_2d__ubuntu_bionic_amd64__binary/ http://build.ros.org/job/Mbin_uA64__find_object_2d__ubuntu_artful_amd64__binary/ http://build.ros.org/job/Mbin_ubv8_uBv8__find_object_2d__ubuntu_bionic_arm64__binary/ http://build.ros.org/job/Mbin_ubhf_uBhf__find_object_2d__ubuntu_bionic_armhf__binary/

Error:

12:21:57 CMake Error at /usr/share/cmake-3.10/Modules/FindQt4.cmake:1320 (message):
12:21:57   Found unsuitable Qt version "" from NOTFOUND, this code requires Qt 4.x
12:21:57 Call Stack (most recent call first):
12:21:57   CMakeLists.txt:47 (FIND_PACKAGE)

Normally it should detect qt5 that should be already installed indirectly by qt_gui_cpp: https://github.com/ros-visualization/qt_gui_core/blob/kinetic-devel/qt_gui_cpp/package.xml#L24

I can reproduce the error with melodic docker desktop (not full):

$ docker run -it osrf/ros:melodic-desktop-bionic
$ cd
$ mkdir catkin_ws
$ cd catkin_ws
$ mkdir src
$ cd src
$ catkin_init_workspace
$ git clone https://github.com/introlab/find-object.git
$ cd ..
$ catkin_make

To solve the problem:

$ apt-get install qtbase5-dev
$ catkin_make

or

$ rosdep install qt_gui_cpp
$ catkin_make

The problem is why qt_gui_cpp doesn't install qtbase5-dev (see package.xml link above)?!?

[matlabbe]

see answer: https://answers.ros.org/question/291892/buildfarm-melodic-build-with-qt_gui_cpp-dependency-doesnt-install-qtbase5-dev/