make scripts python3 compatible

generate_environment_variables.py

src/rosjava_build_tools/__init__.py

src/rosjava_build_tools/create_android_project.py

src/rosjava_build_tools/create_package.py

src/rosjava_build_tools/create_rosjava_project.py

src/rosjava_build_tools/release.py

src/rosjava_build_tools/utils.py