[3.7] bpo-32691: Use mod_spec.parent when running modules with pdb (GH-5510)

Previously the module name was used, which broke relative imports when pdb was run against a plain module or submodule.
(cherry picked from commit 38bfa8418f5d39bcc7478b8f7aef4a632c26172e)

Co-authored-by: Mario Corchero <mariocj89@gmail.com>
3 files changed