fix package description generation script to be compatible with python 2 and 3

Documentation/doc/scripts/pkglist_filter

@@ -1,9 +1,3 @@
 #!/bin/sh
 
-if which python2 2>/dev/null >/dev/null; then 
-    exec python2 ${CMAKE_BINARY_DIR}/pkglist_filter.py "$1"
-elif which python2.7 2>/dev/null >/dev/null; then 
-    exec python2.7 ${CMAKE_BINARY_DIR}/pkglist_filter.py "$1"
-elif which python2.6 2>/dev/null >/dev/null; then 
-    exec python2.6 ${CMAKE_BINARY_DIR}/pkglist_filter.py "$1"
-fi
+exec ${PYTHON_EXECUTABLE} ${CMAKE_BINARY_DIR}/pkglist_filter.py "$1"

Documentation/doc/scripts/pkglist_filter.bat

@@ -1,18 +1,6 @@
 @echo off
 
-@where /q python
-if not errorlevel 1 ( set python=python )
-
-@where /q python2
-if not errorlevel 1 ( set python=python2 )
-
-@where /q python2.6
-if not errorlevel 1 ( set python=python2.6 )
-
-@where /q python2.7
-if not errorlevel 1 ( set python=python2.7 )
-
 :go
-%python% ${CMAKE_BINARY_DIR}/pkglist_filter.py %1
+${PYTHON_EXECUTABLE} ${CMAKE_BINARY_DIR}/pkglist_filter.py %1
 
 @echo on

Documentation/doc/scripts/pkglist_filter.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 
 import codecs
 import re
@@ -28,10 +28,16 @@ def main(argv):
             for l in pkgdesc:
                 do_print = do_print or re.match(".*cgalPkgDescriptionBegin.*", l)
                 if(do_print):
-                    sys.stdout.write(l.encode('utf-8'))
+                  if hasattr(sys.stdout, 'buffer'):
+                    sys.stdout.buffer.write(l.encode('utf-8')) #python3
+                  else:
+                    sys.stdout.write(l.encode('utf-8')) #python2
                 do_print = do_print and (not re.match(".*cgalPkgDescriptionEnd.*", l))
         else:
-            sys.stdout.write(line.encode('utf-8'))
+          if hasattr(sys.stdout, 'buffer'):
+            sys.stdout.buffer.write(line.encode('utf-8')) #python3
+          else:
+            sys.stdout.write(line.encode('utf-8')) #python2
 
 if __name__ == "__main__":
     main(sys.argv)