HPCC-10449 Unicode literals in embedded Python using wrong codepage

Need to tell Python that the source is utf8.

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #5542 from richardkchapman/python-codepage

HPCC-10449 Unicode literals in embedded Python using wrong codepage

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>