I think I found the bug, when I run:

pulumi_gcp.cloudscheduler.Job("what ever",
                              description="whatever",
                              schedule="5 4 * * *",
                              http_target={
                                  'uri': '<https://cloudbuild.googleapis.com/v1/projects/PROJECT_ID/triggers/TRIGGER_ID:run>',
                                  'body': '{}',
                                  'oauth_token': {
                                      'service_account_email': '<mailto:PROJECT_ID@appspot.gserviceaccount.com|PROJECT_ID@appspot.gserviceaccount.com>',
                                      'scope': '<https://www.googleapis.com/auth/cloud-platform>'
                                  }
                              }
                              )

whatever I put in

'body': '{}',

I get

Error creating Job: googleapi: Error 400: Invalid value at 'job.http_target.body' (TYPE_BYTES), Base64 decoding failed for "{}".

Should I open the bug for this or I'm totally missing what should be in body ? The body Regex should be

[a-zA-Z\d_-]{1,500}

Good that I thought of searching slack... You saved me a few hours of pain. Thank you! This should definitely be documented somewhere

yeah, it took me awhile! glad it helped