Add-on: abort submission when job preparation fails

Job preparation (that is, constructing the data to be sent to the Flamenco
API) shouldn't fail, but in case it does, it should stop the rest of the
submission process.

addon/flamenco/operators.py

@@ -451,13 +451,13 @@ class FLAMENCO_OT_submit_job(FlamencoOpMixin, bpy.types.Operator):
         self.blendfile_on_farm = bpathlib.make_absolute(blendfile)
         self._submit_job(context)
 
-    def _prepare_job_for_submission(self, context: bpy.types.Context) -> None:
+    def _prepare_job_for_submission(self, context: bpy.types.Context) -> bool:
         """Prepare self.job for sending to Flamenco."""
 
         self.job = job_submission.job_for_scene(context.scene)
         if self.job is None:
             self.report({"ERROR"}, "Unable to create job")
-            return {"CANCELLED"}
+            return False
 
         propgroup = getattr(context.scene, "flamenco_job_settings", None)
         assert isinstance(propgroup, JobTypePropertyGroup), "did not expect %s" % (
@@ -469,6 +469,9 @@ class FLAMENCO_OT_submit_job(FlamencoOpMixin, bpy.types.Operator):
             propgroup.job_type, self.job, self.blendfile_on_farm
         )
 
+
+        return True
+
     def _submit_job(self, context: bpy.types.Context) -> None:
         """Use the Flamenco API to submit the new Job."""
         assert self.job is not None
@@ -476,7 +479,8 @@ class FLAMENCO_OT_submit_job(FlamencoOpMixin, bpy.types.Operator):
 
         from flamenco.manager import ApiException
 
-        self._prepare_job_for_submission(context)
+        if not self._prepare_job_for_submission(context):
+            return
 
         api_client = self.get_api_client(context)
         try:
@@ -510,7 +514,9 @@ class FLAMENCO_OT_submit_job(FlamencoOpMixin, bpy.types.Operator):
         """
         from flamenco.manager import ApiException
 
-        self._prepare_job_for_submission(context)
+        if not self._prepare_job_for_submission(context):
+            return False
+        assert self.job is not None
 
         api_client = self.get_api_client(context)
         try: