Assign on relation attribute gives cryptic error

[bartv]

h = std::Host(name="test", os=std::linux)
f = std::ConfigFile(host=h, path="a", content="")

h.files.path = "1"

Give the following error:

  File "/home/bart/workspace/inmanta/src/inmanta/ast/statements/assign.py", line 128, in resume
    var = instance.get_attribute(self.attribute_name)
AttributeError: 'list' object has no attribute 'get_attribute'

If the assign become a get (for example std::print(h.files.path) a good error is given:

can not get a attribute path, [std::ConfigFile 7f203aa0d278] is a list (reported in h.files.path (./test.cf:5))