Replace use of deprecated package imp with current importlib

[jafingerhut]

No description provided.

[jafingerhut]

Possible fix for issue #187

Warning: I am poking things with a stick without any kind of deep understanding of the imp and importlib packages. I have tested this on an Ubuntu 20.04 system with python 3.8.10 installed, and several PTF tests I tried worked fine and no longer give the deprecation warnings.

[jafingerhut]

I have looked at the test failure results, but it was not clear to me why the failure occurred.

[fruffy]

Last time I messed around with importlib it was a little bit more complicated than that. This is missing the root folder as path.
I remember you had to use find_spec and load_module instead.

def import_module(root_path, module_name):
    """ Try to import a module and class directly instead of the typical
        Python method. Allows for dynamic imports. """
    finder = importlib.machinery.PathFinder()
    # Unfortunately this does not support Posix paths and silently fails. So we have to use str().
    # This is a standard lib function...
    module_specs = finder.find_spec(str(module_name), [str(root_path)])
    return module_specs.loader.load_module()

[antoninbas]

@fruffy is right here
The test failure means that no test specs can be collected, and this is definitely connected to this change.
You should be able to run the test scripts locally to reproduce.
Additionally this change means that Python 3.1 is required, so this line needs to be changed accordingly:

ptf/setup.cfg

Line 22 in 9c1787d

python_requires = >=2.7, >=3

(note that I don't have an issue with this version requirement).

[jafingerhut]

I may have fixed this. Still poking things with a stick in terms of my knowledge level :-)

[antoninbas]

this is a bit confusing to me: aren't module_name and root_path already strings? looks like they should be based on the call sites below.

when I ran some experiments, it seemed that os.path.splitext for example was returning strings, not path objects

[jafingerhut]

I have removed the comments and calls to str() here after confirming that the way this def import_module was being called, its parameters were always type str anyway.

I suspect those comments were copied and pasted from some other place where Fabian was using it, where that was not the case.

[fruffy]

In this case it makes sense, but the function was initially written to be more general. find_spec does not seem to work if root_path is a Path object. The path has to be explicitly converted. Explicit type checking might be a better approach here.

[antoninbas]

Given the limited use here (2 callers in the same file) and given that we are aligned with find_spec as far as parameter types are concerned, I think the current solution is good enough

[antoninbas]

LGTM
However if I understand the docs correctly, this requires Python 3.4 or above: https://docs.python.org/3/library/importlib.html#importlib.machinery.PathFinder.find_spec
This is perfectly fine, but we need to update the following accordingly:

ptf/setup.cfg

Line 22 in c458186

python_requires = >=3

[jafingerhut]

Added Python >= 3.4 requirement in setup.cfg with commit 7