Cannot install OctoPNP

[claudyus]

Hi all,
using the OctoPrint Version 1.4.0, trying to install the OctoPNP plugin I get the following error:

Installing plugin "OctoPNP" from https://github.com/platsch/OctoPNP/archive/master.zip...
/home/pi/oprint/bin/python2 -m pip --disable-pip-version-check install https://github.com/platsch/OctoPNP/archive/master.zip --no-cache-dir
Looking in indexes: https://pypi.org/simple, https://www.piwheels.org/simple
Collecting https://github.com/platsch/OctoPNP/archive/master.zip
Downloading https://github.com/platsch/OctoPNP/archive/master.zip
Requirement already satisfied: OctoPrint in /home/pi/oprint/lib/python2.7/site-packages (from OctoPNP==0.2) (1.4.0)
Collecting numpy
Downloading https://files.pythonhosted.org/packages/b7/6f/24647f014eef9b67a24adfcbcd4f4928349b4a0f8393b3d7fe648d4d2de3/numpy-1.16.6.zip (5.1MB)
ERROR: Could not find a version that satisfies the requirement opencv-python (from OctoPNP==0.2) (from versions: none)
ERROR: No matching distribution found for opencv-python (from OctoPNP==0.2)
Error!
Could not parse output from pip, see plugin_pluginmanager_console.log for generated output

Thank you

[platsch]

What operating system and CPU architecture are you running?
I just checked on a plain 64bit Ubuntu Linux and can't reproduce the problem.
However: we have seen issues with opencv-python being not available particularly for the RasPi, documented in #3. There also is a workaround suggested in that issue.

[platsch]

I recently updated the OS on two of our printers and run into the same problem.
Unfortunately I still don't have a better solution than installing OpenCV by hand, but I added a note including short instructions to the readme file: https://github.com/platsch/OctoPNP#opencv-on-embedded-hardware-raspberry-pi