Improve error messages regarding track syntax errors (#1908)

* Improve error messages regarding track syntax errors

* lint

* Add space, typo, full stop

esrally/track/loader.py

@@ -1120,6 +1120,11 @@ def read(self, track_name, track_spec_file, mapping_dir):
                     f.write(rendered)
                 self.logger.info("Final rendered track for '%s' has been written to '%s'.", track_spec_file, tmp.name)
                 track_spec = json.loads(rendered)
+            except jinja2.exceptions.TemplateSyntaxError as te:
+                self.logger.exception("Could not load [%s] due to Jinja Syntax Exception.", track_spec_file)
+                msg = f"Could not load '{track_spec_file}' due to Jinja Syntax Exception. "
+                msg += f"The track file ({tmp.name}) likely hasn't been written."
+                raise TrackSyntaxError(msg, te)
             except jinja2.exceptions.TemplateNotFound:
                 self.logger.exception("Could not load [%s]", track_spec_file)
                 raise exceptions.SystemSetupError(f"Track {track_name} does not exist")
@@ -1697,6 +1702,8 @@ def parse_task(
         default_ramp_up_time_period=None,
         completed_by_name=None,
     ):
+        if "operation" not in task_spec:
+            raise TrackSyntaxError("Operation missing from task spec %s in challenge '%s'." % (task_spec, challenge_name))
         op_spec = task_spec["operation"]
         if isinstance(op_spec, str) and op_spec in ops:
             op = ops[op_spec]