Dear maintainer,

Your package fails to build from source against opencv 5.0.0+dfsg-1~exp1,
currently in experimental.

OpenCV 5.0 renames its entire install tree from opencv4 to opencv5 and ships
no compatibility shims:

  * pkg-config: only /usr/lib/<triplet>/pkgconfig/opencv5.pc.  There is no
                opencv4.pc and no opencv.pc.
  * headers:    /usr/include/opencv5/opencv2/..., no /usr/include/opencv4.
  * cmake:      /usr/lib/<triplet>/cmake/opencv5/OpenCVConfig.cmake.  A bare
                find_package(OpenCV) still resolves, but a pinned version
                such as find_package(OpenCV 4.7) no longer matches.
  * modules:    libopencv-calib3d-dev is split into libopencv-calib-dev,
                libopencv-geometry-dev, libopencv-stereo-dev and
                libopencv-ptcloud-dev; libopencv-features2d-dev becomes
                libopencv-features-dev.  The CMake component names change
                with them (features2d -> features).
  * geometry:   the new geometry module is not only a piece of calib3d.  It
                also absorbs shape and contour functions that used to live
                in imgproc -- contourArea, arcLength, approxPolyDP,
                boundingRect, minAreaRect, convexHull and
                getPerspectiveTransform among them -- and opencv2/opencv.hpp
                does not pull in opencv2/geometry.hpp, so code that reached
                those through the umbrella header now needs an explicit
                include of opencv2/geometry.hpp.

os-autoinst fails because ppmclibs/tinycv_impl.cc:18 still includes the
old double-segment legacy header <opencv2/calib3d/calib3d.hpp>, which
OpenCV 5 no longer ships. The g++ invocation already carries -isystem
/usr/include/opencv5, so CMake's module/pkg-config detection is fine;
only this #include is stale, and the build aborts at compile time with
"fatal error: opencv2/calib3d/calib3d.hpp: No such file or directory".
Since libopencv-calib3d-dev is split into calib/geometry/stereo/ptcloud,
there is probably no single flattened <opencv2/calib3d.hpp> replacement
either; the maintainer needs to check which split component(s) provide
the symbols tinycv_impl.cc actually uses (grep ppmclibs/*.cc for the same
#include pattern too), update the #include(s) accordingly, and add the
matching new -dev package(s) to debian/control's Build-Depends.

The same source builds fine in the same chroot against the OpenCV 4.10
packages currently in unstable, so this is specific to OpenCV 5.

The relevant part of the build log follows; the full log is attached.