The error is informative:

You must run the ExpandObjects program for "HVACTemplate:Zone:IdealLoadsAirSystem"

In Eppy, you must pass the expandobjects=True to the run() function (eg: idf1.run(expandobjects=True)). function. By default this parameter is False.

See the docstring of the run function eppy.runner.run_functions:

def run(...)

[...]

expandobjects : bool, optional

Run ExpandObjects prior to simulation (default: False)