Cmake error -DBUILD_PCL_EXAMPLES=true

[PerceptMD]

Required Info
Camera Model	{ R200 / F200 / SR300 / ZR300 / D400 }
Firmware Version	(/)
Operating System & Version	{ Linux (Ubuntu 18.04)
Kernel Version (Linux Only)	(4.15.0-96-generic)
Platform	PC.
SDK Version	{librealsense master bc64e52 }
Language	{/}
Segment	{/}

Issue Description

Previously I have successfully installed the debian librealsense packages via apt-get but now I needed to compile the PCL examples too. So I followed the "Linux manual installation guide".
But calling
cmake ../ -DBUILD_EXAMPLES=true -DBUILD_PCL_EXAMPLES=true
resulted in the following error

CMake Error at wrappers/pcl/pcl-color/CMakeLists.txt:13 (find_package):
By not providing "FindOpenCV.cmake" in CMAKE_MODULE_PATH this project has
asked CMake to find a package configuration file provided by "OpenCV", but
CMake did not find one.

Could not find a package configuration file provided by "OpenCV" with any
of the following names:

OpenCVConfig.cmake
opencv-config.cmake

Add the installation prefix of "OpenCV" to CMAKE_PREFIX_PATH or set
"OpenCV_DIR" to a directory containing one of the above files. If "OpenCV"
provides a separate development package or SDK, be sure it has been
installed.

This could easily be solved by running
sudo apt-get autoremove libopencv-dev python-opencv.
Maybe this could be updated in the installation instructions at wrappers/pcl.

As I did not bother uninstalling the previous installation I also get the following warning now

Severity: Warn
Description: Multiple realsense udev-rules were found! :
1:/etc/udev/rules.d/99-realsense-libusb.rules
2: /lib/udev/rules.d/60-librealsense2-udev-rules.rules
Make sure to remove redundancies!

Any suggestions which version I can delete?

[MartyG-RealSense]

Thanks so much for the documentation feedback! I have put the 'Documentation' label on this case so that it can be tracked by the team members responsible for it.

In regard to the udev rules, I hope that the link below will be helpful.

#4350 (comment)

[PerceptMD]

sudo rm /lib/udev/rules.d/60-librealsense2-udev-rules.rules
deleting "60-librealsense2-udev-rules.rules" fixes the warning and the realsense-viewer still seems to works like a charm.

Thanks for your great support. It is so great to learn about the usage of the realsense SDK here on github that I want to contribute as much as I can.

[MartyG-RealSense]

Awesome, I'm happy to know that your problem was fixed. Your enthusiasm for RealSense is really appreciated. Our community create amazing projects every day. :)

[ev-mp]

@PerceptMD , deleting files from Debians breaks the package integrity.
You should ether delete the stand-alone file or the Debian packages altogether.
Similar to #6153 (comment)

[PerceptMD]

Thanks for the advice.
I've already deleted the "60-librealsense2-udev-rules.rules". So i should purge the Debian package "librealsense2-udev-rules"?