ENH: warn user using python.X with X!=5

Packaging/Files/setup_python.sh

@@ -37,10 +37,12 @@ if [ ! -f "$OTB_PYTHON_EXE" ] ; then
     fi
 fi
 
-python_major_version=$($OTB_PYTHON_EXE -c "import sys;print(sys.version_info[0])")
-python_minor_version=$($OTB_PYTHON_EXE -c "import sys;print(sys.version_info[1])")
-python_patch_version=$($OTB_PYTHON_EXE -c "import sys;print(sys.version_info[2])")
-python_version="$python_major_version.$python_minor_version.$python_patch_version"
+python_version_check() {
+  python_major_version=$($OTB_PYTHON_EXE -c "import sys;print(sys.version_info[0])")
+  python_minor_version=$($OTB_PYTHON_EXE -c "import sys;print(sys.version_info[1])")
+  python_patch_version=$($OTB_PYTHON_EXE -c "import sys;print(sys.version_info[2])")
+  python_version="$python_major_version.$python_minor_version.$python_patch_version"
+}
 
 python_check_failed() {
     printf %s\\n "*****Error occurred during installation******"
@@ -52,7 +54,22 @@ python_check_failed() {
 }
 # Do we need the exact version of python?
 if [ "$python_major_version" -lt 3 ]; then
-python_check_failed
+  OTB_PYTHON_EXE=$(which python3)
+  if [! -f "$OTB_PYTHON_EXE"] ; then
+    python_check_failed
+  else
+    python_version_check()
+    if [ "$python_major_version" -lt 3 ]; then
+      python_check_failed
+    fi
+  fi
+fi
+
+# test for 3.5 only ! and warn user if not!
+if [ "$python_major_version" -eq 5 ]; then
+  printf %s\\n "*****Warning******"
+  printf %s\\n "OTB python bindings require python3.5 but current detected python version is $python_version"
+  printf %s\\n "This case is undefined!"
 fi
 
 python_INSTSONAME=$($OTB_PYTHON_EXE -c "import sys; from distutils import sysconfig; print (sysconfig.get_config_var('INSTSONAME'));")