ENH: Add script for Python3 find_package upgrade

Now that cmake FindPython3 can be universally
used, prefer to only use that set of variable
names for identifying the python executables.

This maintenance script can be used to assist with moving from
the deprecated find_package(PythonInterp) and find_package(PythonLib)
to the preferred find_package(Python3) variable names.

Utilities/Maintenance/FindPython3_ModernizeCMake.sh

@@ -0,0 +1,109 @@
+#!/bin/bash
+
+COMMIT_INFO="COMP: Script to initiate updating to find_package(Python3)
+
+Now that cmake FindPython3 can be universally
+used, prefer to only use that set of variable
+names for identifying the python executables.
+
+Intial procesing with manual cleanup by:
+
+ITK/Utilities/Maintenance/FindPython3_ModernizeCMake.sh
+
+This maintenance script can be used to assist with moving from
+the deprecated find_package(PythonInterp) and find_package(PythonLib)
+to the preferred find_package(Python3) variable names.
+
+------------------------------
+NOTE: This script is intended to make it easier
+       to identify old find_package(PythonInterp
+       uses, but it can not be blindly used.
+       each change must be carefully reviewed.
+"
+
+# Utility functions
+usage() {
+cat << EOF
+Usage: $0
+$COMMIT_INFO
+EOF
+}
+
+die() {
+  echo "$@" 1>&2; exit 1
+}
+
+while test $# -gt 0;
+do
+  opt="$1";
+  case "$opt" in
+    "-h"|"--help")
+      shift;
+      help=true
+      break;;
+    *)
+      break;;
+  esac
+done
+
+if test $help; then
+  usage
+  exit 1
+fi
+
+# Deprecated (since cmake 3.12) variables from the FindPythonInterp
+# PYTHONINTERP_FOUND
+# PYTHON_EXECUTABLE
+# PYTHON_VERSION_STRING
+# PYTHON_VERSION_MAJOR
+# PYTHON_VERSION_MINOR
+# PYTHON_VERSION_PATCH
+# Additional deprecated (since cmake 3.12) variables from the FindPythonLibs
+# PYTHONLIBS_FOUND
+# PYTHON_LIBRARIES
+# PYTHON_INCLUDE_PATH
+# PYTHON_INCLUDE_DIRS
+# PYTHON_DEBUG_LIBRARIES
+# PYTHONLIBS_VERSION_STRING
+# PYTHON_LIBRARY
+# PYTHON_INCLUDE_DIR
+
+
+
+cat > /tmp/temp.sed << EOF
+s/PYTHONINTERP_FOUND/Python3_Interpreter_FOUND/g
+s/PYTHON_EXECUTABLE/Python3_EXECUTABLE/g
+s/PYTHON_VERSION_STRING/Python3_VERSION/g
+s/PYTHON_VERSION_MAJOR/Python3_VERSION_MAJOR/g
+s/PYTHON_VERSION_MINOR/Python3_VERSION_MINOR/g
+s/PYTHON_VERSION_PATCH/Python3_VERSION_PATCH/g
+s/PYTHONLIBS_FOUND/Python3_Development_FOUND/g
+s/PYTHON_LIBRARIES/Python3_LIBRARIES/g
+s/PYTHON_INCLUDE_PATH/Python3_XXXXXXX_INCLUDE_PATH_NO_MAPPING_FOR_THIS_PYTHON.h_PATH_FINDER/g
+s/PYTHON_INCLUDE_DIRS/Python3_INCLUDE_DIRS/g
+s/PYTHON_DEBUG_LIBRARIES/Python3_XXXXX_NO_MAPPING_FOR_THIS_DEBUG_LIBRARIES_FLAG/g
+s/PYTHONLIBS_VERSION_STRING/Python3_VERSION/g
+s/PYTHON_LIBRARY/Python3_XXXXXX_LIBARY__NO_MAPPING_FOR_THIS_/g
+s/PYTHON_INCLUDE_DIR/Python3_XXXXXXX_INCLUDE_DIR_NO_MAPPING_FOR_THIS_PYTHON.h_PATH_FINDER/g
+s/find_package *( *PythonInterp *REQUIRED *)/find_package(Python3 COMPONENTS Interpreter REQUIRED)/g
+s/find_package *( *PythonInterp *)/find_package(Python3 COMPONENTS Interpreter)/g
+s/find_package *( *PythonLibs *)/find_package(Python3 COMPONENTS Development)/g
+s/find_package *( *PythonInterp/find_package(Python3 COMPONENTS Interpreter/g
+s/find_package *( *PythonLibs/find_package(Python3 COMPONENTS Development/g
+s/below_restore_pattern_match_changes_to_original/values/g
+s/SIMPLE_Python3_EXECUTABLE/SIMPLE_PYTHON_EXECUTABLE/g
+s/ITK_WRAP_Python3_XXXXXX_LIBARY__NO_MAPPING_FOR_THIS_/ITK_WRAP_PYTHON_LIBRARY/g
+EOF
+
+if [ $(uname) == "Darwin" ] ; then
+  SEDBIN=gsed
+else
+  SEDBIN=sed
+fi
+
+# Do the replacement
+find . -type f \( -name 'CMakeLists.txt' -o -name '*\.cmake*' \) -exec ${SEDBIN} -i''  -f /tmp/temp.sed {} \;
+
+cat > /tmp/git_message.txt << EOF
+${COMMIT_INFO}
+EOF