Raise error if a non-existing string-type path is passed

[flferretti]

This pull request includes a small change to the get_xml_string function in the src/adam/model/std_factories/std_model.py file. The change simplifies the condition for converting a string to a pathlib.Path object by removing the redundant check for the existence of the path. In this way, an error will be raised when a non-existing string-type path is passed

[xela-95]

@flferretti what happens if we are in the following case: we have an input path variable that is a string and it is a urdf, but without being longer than MAX_PATH? is this an edge case we can forget about?

[flferretti]

is this an edge case we can forget about?

Yes, but we could also think about something like if "<robot" in path:"

[xela-95]

I think that this PR will also be useful to debug the CI failures on the conda-feedstock for the v0.3.1 release: conda-forge/adam-robotics-feedstock#10

[Giulero]

Thanks @flferretti and @xela-95! Can we merge this PR?

[flferretti]

Thanks @flferretti and @xela-95! Can we merge this PR?

Yes, now it's ready for review. I added the modification mentioned in #103 (comment). Thanks!

[flferretti]

@Giulero do you think it would be possible to do a minor release after this? So @xela-95 and me can work on conda-forge/adam-robotics-feedstock#10 and conda-forge/adam-robotics-feedstock#12. Thanks a lot!

[Giulero]

Sure! Let's merge this and release.

[Giulero]

Done! https://github.com/ami-iit/adam/releases/tag/v0.3.2