MAVExplorer requires dependencies that don't come with MAVProxy

[WickedShell]

Installing MAVProxy with pip will install several dependencies, but it doesn't install either wxPython or matplotlib both of which are required to allow MAVExplorer to work. Given that MAVProxy is frequently used on headless machines a better solution might be to distribute MAVExplorer as it's own package (unless there are other things I'm missing that would also improve this).

It mostly just leaves the user in a guessing game of which python package provides the missing import (which is more annoying for wx then matplotlib)

[WickedShell]

Oh, and opencv-python is also needed for the map stuff.