This patch allow that the opencv's build command correctly detects our version
of python, so we can successfully build the python bindings (cv2.so)
--- opencv-4.0.1/cmake/OpenCVDetectPython.cmake.orig	2018-12-22 08:03:30.000000000 +0100
+++ opencv-4.0.1/cmake/OpenCVDetectPython.cmake	2019-01-31 11:33:10.896502978 +0100
@@ -175,7 +175,7 @@ if(NOT ${found})
       endif()
     endif()

-    if(NOT ANDROID AND NOT IOS)
+    if(P4A OR NOT ANDROID AND NOT IOS)
       if(CMAKE_HOST_UNIX)
         execute_process(COMMAND ${_executable} -c "from distutils.sysconfig import *; print(get_python_lib())"
                         RESULT_VARIABLE _cvpy_process
@@ -244,7 +244,7 @@ if(NOT ${found})
                           OUTPUT_STRIP_TRAILING_WHITESPACE)
         endif()
       endif()
-    endif(NOT ANDROID AND NOT IOS)
+    endif(P4A OR NOT ANDROID AND NOT IOS)
   endif()

   # Export return values
--- opencv-4.0.1/modules/python/CMakeLists.txt.orig	2018-12-22 08:03:30.000000000 +0100
+++ opencv-4.0.1/modules/python/CMakeLists.txt	2019-01-31 11:47:17.100494908 +0100
@@ -3,7 +3,7 @@
 # ----------------------------------------------------------------------------
 if(DEFINED OPENCV_INITIAL_PASS)  # OpenCV build

-if(ANDROID OR APPLE_FRAMEWORK OR WINRT)
+if(ANDROID AND NOT P4A OR APPLE_FRAMEWORK OR WINRT)
   ocv_module_disable_(python2)
   ocv_module_disable_(python3)
   return()