def is_python_binding_installed(self):
        """Check if the Python binding has already installed.

        Consider below cases.
        - pip command is not installed.
        - The installed RPM Python binding does not have information
          showed as a result of pip list.
        """
        is_installed = False
        is_install_error = False

        try:
            is_installed = self.is_python_binding_installed_on_pip()
        except InstallError:
            # Consider a case of pip is not installed in old Python (<= 2.6).
            is_install_error = True
        if not is_installed or is_install_error:
            for rpm_dir in self.python_lib_rpm_dirs:
                init_py = os.path.join(rpm_dir, '__init__.py')
                if os.path.isfile(init_py):
                    is_installed = True
                    break

        return is_installed
Check if the Python binding has already installed.

        Consider below cases.
        - pip command is not installed.
        - The installed RPM Python binding does not have information
          showed as a result of pip list.