The documentation files that are generated by installing python-sphinx are missing. I suspect that is cause by the opencv cmake that now checks if the python-sphinx is installed. Since there is no build-depend on it (it wasn't needed earlier) then it just skips creating the PDFs.
How to reproduce:
*BEFORE* installing python-sphinx:
cmake ../path_to_opencv.git
[CUT]
-- Documentation:
-- Build Documentation: NO
-- Sphinx: NO
-- PdfLaTeX compiler: /usr/bin/pdflatex
[CUT]
*AFTER* installing python-sphinx:
[CUT]
-- Documentation:
-- Build Documentation: YES
-- Sphinx: /usr/bin/sphinx-build (ver Sphinx v1.1.3)
-- PdfLaTeX compiler: /usr/bin/pdflatex
[CUT]
Once installed, running make docs should build the pdfs correcly in doc/
opencv2manager.pdf
opencv2refman.pdf
opencv_cheatsheet.pdf
opencv_tutorials.pdf
opencv_user.pdf
This was valid in 2.4.5+dfsg-0ubuntu4
That means that the maintainer of the package should add build depend to python-sphinx before running the make docs...